OLED device with fluoranthene electron injection materials

ABSTRACT

The invention provides an OLED device including a cathode, an anode, and having there between a light-emitting layer, further including, between the cathode and the light emitting layer, a first layer containing a fluoranthene compound including one and only one fluoranthene nucleus and having no aromatic rings annulated to the fluoranthene nucleus, the fluoranthene nucleus having independently selected aromatic groups in the 7,10-positions and an azine group in the 8- or 9-position, provided that the azine group is not a phenanthroline group. The OLED device desirably includes a second layer containing an alkali metal or alkali metal compound, located between the cathode and the first layer. The OLED device can also include a polycyclic aromatic hydrocarbon compound in the first layer or in a third layer located between the first layer and the light-emitting layer. Devices of the invention provide improvement in features such as efficiency and drive voltage.

CROSS-REFERENCE TO RELATED APPLICATION

Reference is made to U.S. patent application Ser. No. 11/924,629 byBegley et al. entitled “OLED DEVICE WITH CERTAIN FLUORANTHENELIGHT-EMITTING DOPANTS,” filed Oct. 26, 2007, U.S. patent applicationSer. No. 11/924,626 by Begley et al. entitled “OLED DEVICE WITH CERTAINFLUORANTHENE HOST,” filed Oct. 26, 2007, U.S. patent application Ser.No. 11/924,631 by Begley et al., entitled “OLED DEVICE WITH FLUORANTHENEELECTRON TRANSPORT MATERIALS,” filed Oct. 26, 2007, and U.S. patentapplication Ser. No. 12/266,802 by Begley et al. entitled“ELECTROLUMINESCENT DEVICE CONTAINING A FLOURANTHENE COMPOUND,” filed onNov. 7, 2008, the disclosures of which are incorporated herein byreference.

FIELD OF THE INVENTION

This invention relates to an organic light-emitting diode (OLED)electroluminescent (EL) device having a light-emitting layer and anelectron-transporting or electron-injecting layer including a specifictype of fluoranthene compound.

BACKGROUND OF THE INVENTION

While organic electroluminescent (EL) devices have been known for overtwo decades, their performance limitations have represented a barrier tomany desirable applications. In simplest form, an organic EL device iscomprised of an anode for hole injection, a cathode for electroninjection, and an organic medium sandwiched between these electrodes tosupport charge recombination that yields emission of light. Thesedevices are also commonly referred to as organic light-emitting diodes,or OLEDs. Representative of earlier organic EL devices are Gurnee et al.U.S. Pat. No. 3,172,862, issued Mar. 9, 1965; Gurnee U.S. Pat. No.3,173,050, issued Mar. 9, 1965; Dresner, “Double InjectionElectroluminescence in Anthracene”, RCA Review, 30, 322, (1969); andDresner U.S. Pat. No. 3,710,167, issued Jan. 9, 1973. The organic layersin these devices, usually composed of a polycyclic aromatic hydrocarbon,were very thick (much greater than 1 μm). Consequently, operatingvoltages were very high, often greater than 100V.

More recent organic EL devices include an organic EL element consistingof extremely thin layers (e.g. <1.0 μm) between the anode and thecathode. Herein, the term “organic EL element” encompasses the layersbetween the anode and cathode. Reducing the thickness lowered theresistance of the organic layers and has enabled devices that operate atmuch lower voltage. In a basic two-layer EL device structure, describedfirst in U.S. Pat. No. 4,356,429, one organic layer of the EL elementadjacent to the anode is specifically chosen to transport holes, andtherefore is referred to as the hole-transporting layer, and the otherorganic layer is specifically chosen to transport electrons and isreferred to as the electron-transporting layer. Recombination of theinjected holes and electrons within the organic EL element results inefficient electroluminescence.

There have also been proposed three-layer organic EL devices thatcontain an organic light-emitting layer (LEL) between thehole-transporting layer and electron-transporting layer, such as thatdisclosed by C. Tang et al. (J. Applied Physics, Vol. 65, 3610 (1989)).The light-emitting layer commonly consists of a host material doped witha guest material, otherwise known as a dopant. Still further, there hasbeen proposed in U.S. Pat. No. 4,769,292 a four-layer EL elementcomprising a hole-injecting layer (HIL), a hole-transporting layer(HTL), a light-emitting layer (LEL) and anelectron-transporting/injecting layer (ETL). These structures haveresulted in improved device efficiency.

EL devices in recent years have expanded to include not only singlecolor emitting devices, such as red, green, and blue, but alsowhite-devices, devices that emit white light. Efficient white lightproducing OLED devices are highly desirable in the industry and areconsidered as a low cost alternative for several applications such aspaper-thin light sources, backlights in LCD displays, automotive domelights, and office lighting. White light producing OLED devices shouldbe bright, efficient, and generally have Commission Internationald'Eclairage (CIE) chromaticity coordinates of about (0.33, 0.33). In anyevent, in accordance with this disclosure, white light is that lightwhich is perceived by a user as having a white color.

Since the early inventions, further improvements in device materialshave resulted in improved performance in attributes such as color,stability, luminance efficiency and manufacturability, e.g., asdisclosed in U.S. Pat. Nos. 5,061,569; 5,409,783; 5,554,450; 5,593,788;5,683,823; 5,908,581; 5,928,802; 6,020,078; and 6,208,077, amongstothers.

Notwithstanding all of these developments, there are continuing needsfor organic EL device components, such as electron transportingmaterials and electron injecting materials, which will provide evenlower device drive voltages and hence lower power consumption, whilemaintaining high luminance efficiencies and long lifetimes combined withhigh color purity.

A useful class of electron-transporting materials is that derived frommetal chelated oxinoid compounds including chelates of oxine itself,also commonly referred to as 8-quinolinol or 8-hydroxyquinoline.Tris(8-quinolinolato)aluminum (III), also known as Alq or Alq₃, andother metal and non-metal oxine chelates are well known in the art aselectron-transporting materials. Tang et al. in U.S. Pat. No. 4,769,292and VanSlyke et al. in U.S. Pat. No. 4,539,507 lower the drive voltageof the EL devices by teaching the use of Alq as an electron transportmaterial in the luminescent layer or luminescent zone. Baldo et al. inU.S. Pat. No. 6,097,147 and Hung et al. in U.S. Pat. No. 6,172,459 teachthe use of an organic electron-transporting layer adjacent to thecathode so that when electrons are injected from the cathode into theelectron-transporting layer, the electrons traverse both theelectron-transporting layer and the light-emitting layer.

Examples of electron-injecting layers include those described in U.S.Pat. Nos. 5,608,287; 5,776,622; 5,776,623; 6,137,223; and 6,140,763, thedisclosures of which are incorporated herein by reference. Anelectron-injecting layer generally consists of a material having a workfunction less than 4.0 eV. The definition of work function can be foundin CRC Handbook of Chemistry and Physics, 70th Edition, 1989-1990, CRCPress Inc., page F-132 and a list of the work functions for variousmetals can be found on pages E-93 and E-94. Typical examples of suchmetals include Li, Na, K, Be, Mg, Ca, Sr, Ba, Y, La, Sm, Gd, Yb. Athin-film containing low work-function alkali metals or alkaline earthmetals, such as Li, Cs, Ca, Mg can be employed for electron-injection.In addition, an organic material doped with these low work-functionmetals can also be used effectively as the electron-injecting layer.Examples are Li- or Cs-doped Alq.

U.S. Pat. No. 6,509,109 and US Publication No. 20030044643, thedisclosures of which are incorporated herein by reference, describe anorganic electroluminescent device wherein the electron injection regioncontains a nitrogen-free aromatic compound as a host material and areducing dopant, such as an alkali metal compound. U.S. Pat. No.6,396,209 describes an electron injection layer of anelectron-transporting organic compound and an organic metal complexcompound containing at least one alkali metal ion, alkali earth metalion, or rare earth metal ion. Additional examples of organic lithiumcompounds in an electron-injection layer of an EL device include USPublication Numbers 2006/0286405, 2002/0086180, 2004/0207318. U.S. Pat.Nos. 6,396,209 and 6,468,676, JP Publication No. 2000-053957, and WOPublication No. 9963023.

Fluoranthene derivatives are well known in the art as being useful aslight-emitting compounds; for example, see US Publication Numbers2005/0271899, 2002/0168544, 2006/0141287, 2006/0238110, and2007/0069198; U.S. Pat. Nos. 6,613,454, 7,183,010, and 7,175,922; EPPatent Numbers 1,718,124 and EP 1,719,748 and WO Publication No.2007039344 describe the use of polymeric fluoranthene derivatives asblue light-emitting dopants.

In particular, examples of 7,10-diaryl-fluoranthene derivatives aslight-emitting compounds have been disclosed in JP Publication Numbers2002-069044 and 2005-320286; US Patent Publication Numbers 2007/00691982005/0067955, and 2006/0246315; U.S. Pat. Nos. 6,803,120 and 6,866,947;WO Publication No. 2007/039344; and R. Tseng et al, Applied PhysicsLetters (2006), 88(9), 09351/1-3. Also, 3,8-Diphenylfluoranthenederivatives are disclosed as light emitters in US Patent Publication No.2007/0063189.

US Publication No. 2002/0022151 describes the use of7,10-diaryl-fluoranthenes with at least one amino group directlysubstituted on the fluoranthene ring in light emitting layers as well ashole and electron transporting layers. US Publication No. 2007/149815describes the use of bis-aminofluoranthenes. US Publication No.2005/0244676 discloses the use of a 3-substituted fluoranthenederivatives with annulated rings in a light-emitting layer incombination with organic lithium salts in an electron-injecting layer.

The use of substituted fluoranthenes in an electron-transporting layeris also known, examples include devices described in US PublicationNumbers 2008/0007160, 2007/0252516, 2006/0257684, and 2006/0097227, andJP Publication No. 2004-09144, the disclosures of which are incorporatedherein by reference.

US Publication No. 2006/0097227 describes phenanthroline derivatives andtheir use in electron-transporting and light-emitting layers of an ELdevice. Included in the disclosure are compounds containing aphenanthroline nucleus bonded to multiple fluoranthene substituents.Likewise, JP Publication No. 2004-09144 discloses diaza fluorenecompounds bonded to several fluoranthene groups. However, these devicesdo not necessarily have all desired EL characteristics in terms of highluminance in combination with low drive voltages.

Notwithstanding all these developments, there remains a need to improveefficiency and reduce drive voltage of OLED devices, as well as toprovide embodiments with other improved features.

SUMMARY OF THE INVENTION

The invention provides an OLED device comprising a cathode, an anode,and having therebetween a light-emitting layer, further including,between the cathode and the light emitting layer, a first layercontaining a fluoranthene compound. The fluoranthene compound includesone and only one fluoranthene nucleus and has no aromatic ringsannulated to the fluoranthene nucleus. The fluoranthene nucleus hasindependently selected aromatic groups in the 7,10-positions and anazine group in the 8- or 9-position, provided that the azine group isnot a phenanthroline group.

In a second embodiment, the OLED device includes an alkali metal oralkali metal compound wherein the alkali metal or alkali metal compoundis present in the first layer or in a second layer located between thecathode and the first layer.

In a third embodiment, the OLED device includes a polycyclic aromatichydrocarbon compound which is present in the first layer, in addition tothe fluoranthene compound, or in a third layer located between the firstlayer and the light-emitting layer.

Devices of the invention provide improvement in features such asefficiency and drive voltage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic cross-sectional view of one embodiment of theOLED device of the present invention. It will be understood that FIG. 1is not to scale since the individual layers are too thin and thethickness differences of various layers are too great to permitdepiction to scale.

DETAILED DESCRIPTION OF THE INVENTION

The invention is generally as described above. An OLED device of theinvention is a multilayer electroluminescent device comprising acathode, an anode, light-emitting layer(s) (LEL), electron-transportinglayer(s) (ETL) and electron-injecting layer(s) (EIL) and optionallyadditional layers such as hole-injecting layer(s), hole-transportinglayer(s), exciton-blocking layer(s), spacer layer(s), connectinglayer(s) and hole-blocking layer(s).

A first layer between the light-emitting layer and the cathode includesa fluoranthene compound. The fluoranthene compound facilitates thetransport of electrons from the cathode to the light emitting layer. Forexample, the first layer can be an electron-injecting layer. Thethickness of electron-injecting layer is often in the range of 0.1 nm to50 nm, but preferably 0.4 nm to 10 nm, and more preferable from 1 nm to8 nm. The electron-injecting layer can be subdivided further into two ormore sub-layers, for example, it can be divided into a first (EIL1) anda second (EIL2) injection layer and it can be further divided. In oneembodiment, the thickness of the first layer is 20 nm or less, 10 nm orless, or even 5 nm or less. The thickness of the layers can becontrolled and measured during device fabrication using calibratedthickness monitors, for example, an INFICON IC/5 Deposition Controller,made by Inficon Inc., Syracuse, N.Y.

The fluoranthene compound is also useful in electron-transporting layers(ETLs). The electron-transporting layer is present between thelight-emitting layer and the cathode and often has a thickness of 1-100nm, or 5-50 nm, or more frequently 10-40 nm. When an electron-injectionlayer is present, the electron-transporting layer (ETL) is locatedbetween the electron-injecting layer and the light emitting layer (LEL).

The fluoranthene compound can comprise 100% of the first layer or therecan be other components in the layer, in which case the fluoranthenecompound can be present at a level of substantially less than 100% ofthe layer, for instance it can be present at 90% by volume, 80%, 70%, or50% by volume, or even less. Desirably, when other components arepresent in the layer they also have good electron-transportingproperties.

In one embodiment, a fluoranthene compound is present in at least oneelectron-injecting layer or electron-transporting layer that is anon-luminescent layer; that is, it should provide less than 25% of thetotal device emission. Ideally, it should have substantially no lightemission.

The fluoranthene compounds of the invention contain only onefluoranthene nucleus and the fluoranthene nucleus contains only 4annulated rings.

The fluoranthene compounds contain no additional rings annulated to thenucleus. Annulated rings are those rings that share a common ring bondbetween any two carbon atoms of the fluoranthene nucleus. Illustrativeexamples of compounds containing a fluoranthene nucleus with one or moreannulated rings and that are excluded from the invention are shownbelow.

The fluoranthene nucleus numbering sequence is illustrated below. Thefluoranthene compound includes aromatic groups in the 7,10-positions,which can be the same or different. The aromatic groups can besubstituted or unsubstituted and can contain annulated rings. Examplesof useful aromatic groups include heteroaromatic groups such as pyridylgroups, and quinolyl groups. In one desirable embodiment, the aromaticgroups are selected from carbocyclic aromatic rings having 6-24 carbonssuch as, for example, phenyl groups, tolyl groups, or naphthyl groups.The fluoranthene nucleus can be further substituted, for example, withadditional aromatic groups, such as phenyl groups and naphthyl groups,or, for example, alkyl groups having 1-24 carbon atoms such as methylgroups and t-butyl groups.

The fluoranthene compound includes an azine group directly bonded to thefluoranthene nucleus at the 8- or 9-position. In some embodiments, thefluoranthene compound has independently selected azine groups in boththe 8- and 9-positions. An azine group is a benzene nucleus in which atleast one of the carbon atoms has been replaced with a nitrogen atom,with the understanding that more than one carbon atom can be replacedwith a nitrogen. The azine group is not a phenanthroline group.Illustrative suitable examples of azine groups include a 2-pyridinegroup, a 3-pyridine group, a 4-pyridine group, a pyrazine group, apyrimidine group, a 1,2,3-triazine group, a 1,2,4-triazine group, and a1,3,5-triazine group. Illustrative examples of azine groups are alsodrawn below.

In one desirable embodiment, the azine group contains additional fusedrings provided the additional fused rings do not contain heteroatoms. Inanother embodiment, the azine group contains no more than two fusedrings, for example a quinoline group. In a further embodiment, the azinegroup contains no fused rings. In a still further embodiment, the azinegroup is a pyridine group, a pyrimidine group, or a pyrazine group;illustrative examples include 5-phenylpyrid-3-yl, 2-methyl-pyrimid-5-yl,quinol-2-yl group and isoquino-3-ly. In another suitable embodiment, theazine group is a pyridine group, a pyrimidine group or a pyrazine group,which contains no more than two fused rings, for example, a quinlo-2-ylgroup. In a further embodiment, the azine group is a pyridine group, apyrimidine group or a pyrazine group, and the azine group contains nofused rings. In another desirable embodiment, the azine group is apyrid-3-yl or pyrid-4-yl group containing no fused rings. It should beunderstood that the use of the “-yl” suffix indicates the point ofattachment of the azine group to the fluoranthene nucleus. For example,pyrid-3-yl indicates a pyridine ring having a nitrogen in the 1-positionand attached to the fluoranthene nucleus in the 3-position of thepyridine ring.

The fluoranthene nucleus contains four annulated aromatic rings alsocommonly referred to as fused aromatic rings. In one desirableembodiment, the fluoranthene compound, which has a fluoranthene nucleusand substituents, contains less than a total of ten fused aromaticrings, or less than eight fused aromatic rings, or even less than sixfused aromatic rings.

In another suitable embodiment, the fluoranthene compound is representedby Formula (I).

In Formula (I) each Ar₁ and Ar₂ is independently selected and representsan aromatic ring group such as a phenyl group or naphthyl group. In onesuitable embodiment, Ar₁ and Ar₂ are independently selected aryl ringgroups containing 6 to 24 carbon atoms. In another desirable embodiment,Ar₁ and Ar₂ are the same.

R₁-R₇ are individually selected from hydrogen or a substituent group,provided that two adjacent R₁-R₇ substituents cannot join to form anaromatic ring system fused to the fluoranthene nucleus. Likewise, Ar₁and R₁ as well as Ar₂ and Az cannot combine to form fused rings. In oneembodiment, R₁-R₇ each independently represents hydrogen, an alkylgroup, or an aryl group. Suitably R₁-R₇ represent independentlyhydrogen, an aryl group having 6-24 carbon atoms such as a phenyl groupor a naphthyl group, or an alkyl groups from 1-24 carbon atoms. In afurther embodiment, each of R₁-R₇ represents hydrogen.

Az represents an azine group, which can be further substituted, howeverit does not represent a phenanthroline group. Examples of suitable azinegroups have been described previously.

In another embodiment, R₁ also represents an azine group, which can bethe same as or different from the Az group. In one desirable embodiment,R₁ and Az are the same.

In another embodiment, the fluoranthene compound is represented byFormula (II).

In Formula (II), R₁ represents hydrogen or a substituent group and R₂-R₇are individually selected from hydrogen or a substituent group providedadjacent R₂-R₇ substituents do not join to form an aromatic ring systemfused to the fluoranthene nucleus. Suitable groups include alkyl groupshaving 1-24 carbon atoms such as methyl or t-butyl groups, and arylgroups having 6-24 carbon atoms such as phenyl groups. In one embodimentR₁ represents hydrogen. In another embodiment, each of R₂-R₇ representshydrogen.

R represents a substituent, provided adjacent substituents can join toform a ring group such as a fused benzene ring, and n and m areindependently 0-5. Suitably, R can represent an alkyl group having 1-24carbon atoms or an aryl group having 6-24 carbon atoms.

Az has been described previously. In one suitable embodiment Az includesmore than one nitrogen, for example, Az can represent a pyrimidine ringgroup or a pyrazine ring group. In another embodiment, Az includes onlyone nitrogen, for example, a pyrid-3-yl group. In a further embodiment,Az contains no more than one fused ring, for example, Az can represent aquinoline ring group. In another embodiment, R₁ also represents anindependently selected azine group.

Suitable fluoranthene compounds can be prepared utilizing knownsynthetic methods or modification thereof, for example, by methodssimilar to those described by Marappan Velusamy et al., Dalton Trans.,3025-3034 (2007) or P. Bergmann et al., Chemische Berichte, 828-35(1967). In general, fluoranthenes having aromatic groups in the 7, 10positions are easier to synthesize than fluoranthenes lacking this typeof substitution. An example of one general synthetic route is shownbelow (Scheme A). Compound 1 is reacted with ketone 2 in the presence ofbase, such as potassium hydroxide, to yield 3. Treatment of 3 with theacetylene 4 at high temperatures in a high-boiling solvent such aso-dichlorobenzene or diphenyl ether forms the fluoranthene compound 5.

It should be understood that in the synthesis of organic molecules,particular synthetic pathways can give rise to molecules, eitherexclusively or as mixtures of molecules, which have the same molecularformulae but differ only in having a particular substituent located at adifferent site somewhere in the molecule. In other words, the moleculesor the molecules in the mixtures can differ from each other by thearrangement of their substituents or more generally, the arrangement ofsome of their atoms in space. When this occurs, the materials arereferred to as isomers. A broader definition of an isomer can be foundin Grant and Hackh's Chemical Dictionary, Fifth Edition, McGraw-HillBook Company, page 313. The synthetic pathway outlined in Scheme A is anexample of a pathway that can give rise to isomers by virtue of how theacetylene molecule, 4, reacts spatially with compound 3, when compound 3is unsymmetrical. It should be realized that the current inventionincludes not only examples of molecules represented by generic FormulaeI and II and their specific molecular examples, but also includes allthe isomers associated with these structures. In addition, examples ofcompounds of the invention and their isomers are not limited to thosederived from symmetrical or unsymmetrical compounds of general structure3, but can also include other frameworks and methods of preparation thatare useful in producing compounds of Formulae I and II. In someembodiments, it is desirable to use a fluoranthene compound thatconsists of a mixture of isomers.

Illustrative, non-limiting, examples of useful fluoranthene compoundsare shown below.

In one highly desirable embodiment of the invention, there isadditionally present a second layer, located between the first layer andthe cathode. In one embodiment, the second layer is contiguous to thefirst layer. For example, the second layer can be an electron-injectinglayer. The second layer contains at least one material chosen fromalkali metals, alkali metal compounds, alkaline earth metals, oralkaline earth metal compounds, or combinations thereof. The term “metalcompounds” includes organometallic complexes, metal-organic salts, andinorganic salts, oxides and halides. Among the class of metal-containingmaterials, Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, La, Ce, Sm, Eu, Tb, Dy, orYb, and their compounds, are particularly useful.

In another desirable embodiment, the second layer contains an alkalimetal or an alkali metal compound. As an illustrative example, a usefulOLED device includes the first layer corresponding to a firstelectron-injecting layer (EIL1) containing a compound of Formula (I);and the second layer, located between the first layer and the cathode,corresponding to a second electron-injecting layer (EIL2), whichcontains an alkali metal compound such as LiF. In a further example, theEIL2 is a thin layer of 5 nm or less that contains Li metal.

In one suitable embodiment, the first layer also contains, in additionto the fluoranthene compound, at least one material chosen from alkalimetals, alkali metal compounds, alkaline earth metals, or alkaline earthmetal compounds, or combinations thereof In another embodiment, thefirst layer contains at least one alkali metal or alkali metal compoundin addition to the fluoranthene compound. The % volume ratio of alkalimetal to fluoranthene compound can be anywhere from 0.1% to 10%,typically 0.5% to 8%, suitably 0.5% to 5%. The % volume ratio of alkalimetal compound to fluoranthene compound can be anywhere from 0.1% to99%, typically 0.5% to 95%, more suitably 10% to 90% and most desirably,30 to 70%. The first layer can include additional materials.

Alkali metals belong to Group 1 of the periodic table. Of these, lithiumis highly preferred. The alkali metal compound can be inorganic or anorganometallic compound. For example, inorganic lithium materials suchas Li metal or LiF are particularly useful. Organic lithium compoundssuch as those according to Formula (IIIa) are also useful in an EIL.(Li⁺)_(m)(Q)_(n)  Formula (IIIa)In Formula (IIIa), Q is an anionic organic ligand; and m and n areindependently selected integers selected to provide a neutral charge onthe complex.

The anionic organic ligand Q is most suitably monoanionic and containsat least one ionizable site consisting of oxygen, nitrogen or carbon. Inthe case of enolates or other tautomeric systems containing oxygen, itwill be considered and drawn with the lithium bonded to the oxygenalthough the lithium can, in fact, be bonded elsewhere to form achelate. It is also desirable that the ligand contains as at least onenitrogen atom that can form a coordinate or dative bond with thelithium. The integers m and n can be greater than 1 reflecting a knownpropensity for some organic lithium compounds to form cluster complexes.

In another embodiment, Formula (IIIb) represents the organic lithiumcompound.

In Formula (IIIb), Z and the dashed arc represent two to four atoms andthe bonds necessary to complete a 5- to 7-membered ring with the lithiumcation; each A represents hydrogen or a substituent and each Brepresents hydrogen or an independently selected substituent on the Zatoms, provided that two or more substituents can combine to form afused ring or a fused ring system; and j is 0-3 and k is 1 or 2; and mand n are independently selected integers selected to provide a neutralcharge on the complex.

Of compounds of Formula (IIIb), it is most desirable that the A and Bsubstituents together form an additional ring system. This additionalring system can further contain additional heteroatoms to form amultidentate ligand with coordinate or dative bonding to the lithium.Desirable heteroatoms are nitrogen or oxygen.

In Formula (IIIb), it is preferred that the oxygen shown is part of ahydroxyl, carboxy or keto group. Examples of suitable nitrogen ligandsare 8-hydroxyquinoline, 2-hydroxymethylpyridine, pipecolinic acid or2-pyridinecarboxylic acid.

Illustrative examples of useful organic alkali metal compounds includethe following.

In a further desirable embodiment, the OLED device includes a thirdlayer located between the first layer and the light-emitting layer,wherein the third layer includes a polycyclic aromaticelectron-transporting compound. In one embodiment, the third layer iscontiguous to the first layer. Both the first and third layers cancontain independently selected polycyclic aromatic electron-transportingcompounds. The polycyclic aromatic compound can be a hydrocarbon or aheterocycle and includes at least 3 fused rings. In one embodiment, thepolycyclic aromatic compound includes a total of at least 6 aromaticrings including at least 3 fused rings. Examples include derivatives oftetracene, pyrene, coronene, chrysene, anthracene, phenanthroline, andbathophenanthroline, diphenylanthracene, fluoranthene, and phenanthrene.Especially useful are polycyclic aromatic hydrocarbons includinganthracene derivatives and fluoranthene derivatives. In one embodiment,the third layer also contains at least one material chosen from alkalimetals, alkali metal compounds, alkaline earth metals, or alkaline earthmetal compounds, or combinations thereof As an illustrative example, auseful OLED device includes the first layer, present between thelight-emitting layer (LEL) and the cathode, which corresponds to a firstelectron-injecting layer (EIL1) and contains a fluoranthene compound.The second layer, containing an alkali metal or an alkali metal compoundand corresponding to a second electron-injecting layer (EIL2) is presentbetween the first layer and the cathode. The third layer correspondingto an electron-transporting layer (ETL) is present between the firstlayer and the light-emitting layer and includes a polycyclic aromaticelectron-transporting compound. During operation, electrons flow fromthe cathode to the EIL2 and then are transported into the EIL1 and fromthere into the ETL and finally to the LEL.

During this process electrons are transferred from the fluoranthenecompound of the first layer to the polycyclic aromatic compound of thethird layer. In order to facilitate this transfer, it is desirable tochoose the polycyclic aromatic compound such that its LUMO (LowestUnoccupied Molecular Orbital) energy level is near the LUMO value of thefluoranthene compound. Desirably, the difference in LUMO energy is anabsolute value of 0.3 eV or less, or suitably 0.2 eV or less, anddesirably an absolute value of 0.1 eV or less. In a further embodiment,the LUMO energy of the polycyclic aromatic hydrocarbon is the same as orlower (more negative) than that of the fluoranthene compound, forexample, lower by 0.05 eV or even 0.1 eV lower or more. LUMO and HOMOenergy levels can be determined from redox properties of molecules,which can be measured by well-known literature procedures, such ascyclic voltammetry (CV) and Osteryoung square-wave voltammetry (SWV).For a review of electrochemical measurements, see J. O. Bockris and A.K. N. Reddy, Modern Electrochemistry, Plenum Press, New York; and A. J.Bard and L. R. Faulkner, Electrochemical Methods, John Wiley & Sons, NewYork, and references cited therein.

LUMO and HOMO energy levels can also be calculated. Typical calculationsare carried out by using the B3LYP method as implemented in the Gaussian98 (Gaussian, Inc., Pittsburgh, Pa.) computer program. The basis set foruse with the B3LYP method is defined as follows: MIDI! for all atoms forwhich MIDI! is defined, 6-31 G* for all atoms defined in 6-31 G* but notin MIDI!, and either the LACV3P or the LANL2DZ basis set andpseudopotential for atoms not defined in MIDI! or 6-31 G*, with LACV3Pbeing the preferred method. For any remaining atoms, any published basisset and pseudopotential can be used. MIDI!, 6-31 G* and LANL2DZ are usedas implemented in the Gaussian98 computer code and LACV3P is used asimplemented in the Jaguar 4.1 (Schrodinger, Inc., Portland Oreg.)computer code.

The third layer can also contain organic lithium compounds of Formula(IIIa) or (IIIb) at a level of 0.1-99%, typically 0.5%-95%, moresuitably 10 to 90%, and preferably at a level of 30 to 70%. Likewise,the third layer can contain inorganic alkali metal compounds such a Limetal or LiF, typically present at a level of 0.1-20%, suitably at alevel of 0.5-10%, and often at a level of 1-5%. The percentages givenare based on the volume of the layer.

Especially suitable polycyclic electron-transporting aromatic compoundsinclude anthracene compounds according to Formula (IV).

In Formula (IV), R¹ and R⁶ each independently represent an aryl grouphaving 6-24 carbon atoms such as a phenyl group or a naphthyl group.R²-R⁵ and R⁷-R¹⁰ are each independently chosen from hydrogen, alkylgroups from 1-24 carbon atoms or aromatic groups from 6-24 carbon atoms.

In one suitable embodiment R¹ and R⁶ each represent an independentlyselected phenyl group, biphenyl group, or naphthyl group. R³ representsa hydrogen or a phenyl or naphthyl group. R², R⁴, R⁵, and R⁷-R¹⁰represent hydrogen.

Illustrative examples of useful anthracenes are listed below.

Fluoranthenes according to Formula (V) are also suitable polycyclicelectron-transporting aromatic compounds.

In Formula (V), R¹¹-R²⁰ are independently chosen from hydrogen, alkylgroups from 1-24 carbon atoms or aromatic groups from 6-24 carbon atomsprovided adjacent groups can combine to form fused aromatic rings. Inone desirable embodiment, R¹¹ and R¹⁴ represent aryl groups and R¹², R¹³and R¹⁵-R²⁰ are independently chosen from hydrogen, alkyl groups from1-24 carbon atoms or aromatic groups from 6-24 carbon atoms providedadjacent groups cannot combine to form fused aromatic rings.

Especially suitable fluoranthene derivatives are those described in U.S.patent application Ser. No. 11/924,631, by William J. Begley et al.,filed Oct. 26, 2007, entitled “OLED DEVICE WITH FLUORANTHENE ELECTRONTRANSPORT MATERIALS,” the disclosure of which is incorporated herein byreference.

In Formula (VI) Ar represents the aromatic rings containing 6 to 24carbon atoms substituted on the fluoranthene nucleus and can be the sameor different; and R₁-R₈ are individually selected from hydrogen andaromatic rings containing 6 to 24 carbon atoms with the proviso that notwo adjacent R₁-R₈ substituents can join to form a ring annulated to thefluoranthene nucleus.

In Formula (VI), the Ar group(s) are carbocyclic groups. The Ar group(s)cannot be fused with the floranthene nucleus and are connected only byone single bond. Preferred Ar groups are phenyl or naphthyl with phenylbeing particularly preferred. Derivatives where the Ar groups are thesame are also desirable.

In Formula (VII), R₁, R₂, R₃, and R₄ are independently hydrogen or anaromatic group containing 6 to 24 carbon atoms with the proviso that anyadjacent R₁-R₄ is not part of an annulated aromatic ring system; R ishydrogen or an optional substituent; and n and m are independently 0-5.

In some embodiments, it can be desirable to use isomeric mixtures offluoranthene derivatives. The mixture can prevent undesirablecrystallization.

Illustrative examples of useful electron-transporting fluoranthenederivatives are shown below.

FIG. 1 shows one embodiment of the invention in whichelectron-transporting (ETL, 136) and electron-injecting layers (EIL,138) are present. An optional hole-blocking layer (HBL, 135) is shownbetween the light-emitting layer and the electron-transporting layer.The figure also shows an optional hole-injecting layer (HIL, 130). Inanother embodiment, there is no hole-blocking layer (HBL, 135) locatedbetween the ETL and the LEL. In yet other embodiments, theelectron-injecting layer can be subdivided into two or more sublayers.

In one illustrative example, the OLED device has no hole-blocking layerand only one hole-injecting, electron-injecting andelectron-transporting layer. The fluoranthene compound is present in theEIL (138) and an organic lithium compound is also present in the EIL anda polycyclic electron-transporting aromatic compound is present in theETL (136). In another illustrative example, the EIL (138) is furtherdivided into two sublayers (not shown), a first electron-injecting layer(EIL1) adjacent to the ETL (136) and a second electron-injecting layer(EIL2) located between the EIL1 and the cathode. The fluoranthenecompound is present in the EIL1 and a lithium metal compound is presentin the EIL2 and a polycyclic aromatic electron-transporting compound ispresent in the ETL (136). For example, in some embodiments Li metal canbe present in EIL2 or EIL1 or both.

Examples of preferred combinations of the invention are those whereinthe fluoranthene compound is selected from Inv-1, Inv-2, Inv-3, Inv-4,and Inv-5 or mixtures thereof, the alkali metal compound is selectedfrom Li metal, LiF, AM-1, AM-2, and AM-3 or mixtures thereof, and thepolycyclic aromatic electron-transporting compound (when present) isselected from FA-1, FA-2, FA-3, FA-4, P-1, P-2, P-3, and P-4 or mixturesthereof.

In one suitable embodiment the EL device includes a way for emittingwhite light, which can include complimentary emitters, a white emitter,or a filtering device. This invention can be used in so-called stackeddevice architecture, for example, as taught in U.S. Pat. Nos. 5,703,436and 6,337,492. Embodiments of the current invention can be used instacked devices that comprise solely fluorescent elements to producewhite light. The device can also include combinations of fluorescentemitting materials and phosphorescent emitting materials (sometimesreferred to as hybrid OLED devices). To produce a white emitting device,ideally the hybrid fluorescent/phosphorescent device would comprise ablue fluorescent emitter and proper proportions of a green and redphosphorescent emitter, or other color combinations suitable to makewhite emission. However, hybrid devices having non-white emission canalso be useful by themselves. Hybrid fluorescent/phosphorescent elementshaving non-white emission can also be combined with additionalphosphorescent elements in series in a stacked OLED. For example, whiteemission can be produced by one or more hybrid blue fluorescent/redphosphorescent elements stacked in series with a green phosphorescentelement using p/n junction connectors as disclosed in Tang et al. inU.S. Pat. No. 6,936,961.

In one desirable embodiment the EL device is part of a display device.In another suitable embodiment the EL device is part of an area lightingdevice.

The EL device of the invention is useful in any device where stablelight emission is desired such as a lamp or a component in a static ormotion imaging device, such as a television, cell phone, DVD player, orcomputer monitor.

As used herein and throughout this application, the term carbocyclic andheterocyclic rings or groups are generally as defined by the Grant &Hackh's Chemical Dictionary, Fifth Edition, McGraw-Hill Book Company. Acarbocyclic ring is any aromatic or non-aromatic ring system containingonly carbon atoms and a heterocyclic ring is any aromatic ornon-aromatic ring system containing both carbon and non-carbon atomssuch as nitrogen (N), oxygen (O), sulfur (S), phosphorous (P), silicon(Si), gallium (Ga), boron (B), beryllium (Be), indium (In), aluminum(Al), and other elements found in the periodic table useful in formingring systems. For the purpose of this invention, also included in thedefinition of a heterocyclic ring are those rings that includecoordinate bonds. The definition of a coordinate or dative bond can befound in Grant & Hackh's Chemical Dictionary, pages 91 and 153. Inessence, a coordinate bond is formed when electron rich atoms such as Oor N, donate a pair of electrons to electron deficient atoms or ionssuch as aluminum, boron or alkali metal ions such as Li⁺, Na⁺, K⁺ andCs⁺. One such example is found in tris(8-quinolinolato)aluminum(III),also referred to as Alq, wherein the nitrogen on the quinoline moietydonates its lone pair of electrons to the aluminum atom thus forming theheterocycle and hence providing Alq with a total of 3 fused rings. Thedefinition of a ligand, including a multidentate ligand, can be found inGrant & Hackh's Chemical Dictionary, pages 337 and 176, respectively.

Unless otherwise specifically stated, use of the term “substituted” or“substituent” means any group or atom other than hydrogen. Additionally,when the term “group” is used, it means that when a substituent groupcontains substitutable hydrogen, it is also intended to encompass notonly the substituent's unsubstituted form, but also its form furthersubstituted with any substituent group or groups as herein mentioned, solong as the substituent does not destroy properties necessary for deviceutility. Suitably, a substituent group can be halogen or can be bondedto the remainder of the molecule by an atom of carbon, silicon, oxygen,nitrogen, phosphorous, sulfur, selenium, or boron. The substituent canbe, for example, halogen such as chloro, bromo or fluoro; nitro;hydroxyl; cyano; carboxyl; or groups which can be further substituted,such as alkyl, including straight or branched chain or cyclic alkyl,such as methyl, trifluoromethyl, ethyl, t-butyl,3-(2,4-di-t-pentylphenoxy)propyl, and tetradecyl; alkenyl such asethylene, 2-butene; alkoxy, such as methoxy, ethoxy, propoxy, butoxy,2-methoxyethoxy, sec-butoxy, hexyloxy, 2-ethylhexyloxy, tetradecyloxy,2-(2,4-di-t-pentylphenoxy)ethoxy, and 2-dodecyloxyethoxy; aryl such asphenyl, 4-t-butylphenyl, 2,4,6-trimethylphenyl, naphthyl; aryloxy suchas phenoxy, 2-methylphenoxy, alpha- or beta-naphthyloxy, and 4-tolyloxy;carbonamido such as acetamido, benzamido, butyramido, tetradecanamido,alpha-(2,4-di-t-pentyl-phenoxy)acetamido,alpha-(2,4-di-t-pentylphenoxy)butyramido,alpha-(3-pentadecylphenoxy)-hexanamido,alpha-(4-hydroxy-3-t-butylphenoxy)-tetradecanamido,2-oxo-pyrrolidin-1-yl, 2-oxo-5-tetradecylpyrrolin-1-yl,N-methyltetradecanamido, N-succinimido, N-phthalimido,2,5-dioxo-1-oxazolidinyl, 3-dodecyl-2,5-dioxo-1-imidazolyl, andN-acetyl-N-dodecylamino, ethoxycarbonylamino, phenoxycarbonylamino,benzyloxycarbonylamino, hexadecyloxycarbonylamino,2,4-di-t-butylphenoxycarbonylamino, phenylcarbonylamino,2,5-(di-t-pentylphenyl)carbonylamino, p-dodecyl-phenylcarbonylamino,p-tolylcarbonylamino, N-methylureido, N,N-dimethylureido,N-methyl-N-dodecylureido, N-hexadecylureido, N,N-dioctadecylureido,N,N-dioctyl-N′-ethylureido, N-phenylureido, N,N-diphenylureido,N-phenyl-N-p-tolylureido, N-(m-hexadecylphenyl)ureido,N,N-(2,5-di-t-pentylphenyl)-N′-ethylureido, and t-butylcarbonamido;sulfonamido such as methylsulfonamido, benzenesulfonamido,p-tolylsulfonamido, p-dodecylbenzenesulfonamido,N-methyltetradecylsulfonamido, N,N-dipropyl-sulfamoylamino, andhexadecylsulfonamido; sulfamoyl such as N-methylsulfamoyl,N-ethylsulfamoyl, N,N-dipropylsulfamoyl, N-hexadecylsulfamoyl,N,N-dimethylsulfamoyl, N-[3-(dodecyloxy)propyl]sulfamoyl,N-[4-(2,4-di-t-pentylphenoxy)butyl]sulfamoyl,N-methyl-N-tetradecylsulfamoyl, and N-dodecylsulfamoyl; carbamoyl suchas N-methylcarbamoyl, N,N-dibutylcarbamoyl, N-octadecylcarbamoyl,N-[4-(2,4-di-t-pentylphenoxy)butyl]carbamoyl,N-methyl-N-tetradecylcarbamoyl, and N,N-dioctylcarbamoyl; acyl such asacetyl, (2,4-di-t-amylphenoxy)acetyl, phenoxycarbonyl,p-dodecyloxyphenoxycarbonyl methoxycarbonyl, butoxycarbonyl,tetradecyloxycarbonyl, ethoxycarbonyl, benzyloxycarbonyl,3-pentadecyloxycarbonyl, and dodecyloxycarbonyl; sulfonyl such asmethoxysulfonyl, octyloxysulfonyl, tetradecyloxysulfonyl,2-ethylhexyloxysulfonyl, phenoxysulfonyl,2,4-di-t-pentylphenoxysulfonyl, methylsulfonyl, octylsulfonyl,2-ethylhexylsulfonyl, dodecylsulfonyl, hexadecylsulfonyl,phenylsulfonyl, 4-nonylphenylsulfonyl, and p-tolylsulfonyl; sulfonyloxysuch as dodecylsulfonyloxy, and hexadecylsulfonyloxy; sulfinyl such asmethylsulfinyl, octylsulfinyl, 2-ethylhexylsulfinyl, dodecylsulfinyl,hexadecylsulfinyl, phenylsulfinyl, 4-nonylphenylsulfinyl, andp-tolylsulfinyl; thio such as ethylthio, octylthio, benzylthio,tetradecylthio, 2-(2,4-di-t-pentylphenoxy)ethylthio, phenylthio,2-butoxy-5-t-octylphenylthio, and p-tolylthio; acyloxy such asacetyloxy, benzoyloxy, octadecanoyloxy, p-dodecylamidobenzoyloxy,N-phenylcarbamoyloxy, N-ethylcarbamoyloxy, and cyclohexylcarbonyloxy;amine such as phenylanilino, 2-chloroanilino, diethylamine,dodecylamine; imino such as 1(N-phenylimido)ethyl, N-succinimido or3-benzylhydantoinyl; phosphate such as dimethylphosphate andethylbutylphosphate; phosphite such as diethyl and dihexylphosphite; aheterocyclic group, a heterocyclic oxy group or a heterocyclic thiogroup, each of which can be substituted and which contain a 3 to 7membered heterocyclic ring composed of carbon atoms and at least onehetero atom selected from the group including oxygen, nitrogen, sulfur,phosphorous, or boron, such as 2-furyl, 2-thienyl, 2-benzimidazolyloxyor 2-benzothiazolyl; quaternary ammonium such as triethylammonium;quaternary phosphonium such as triphenylphosphonium; and silyloxy, suchas trimethylsilyloxy.

If desired, the substituents can themselves be further substituted oneor more times with the described substituent groups. The particularsubstituents used can be selected by those skilled in the art to attaindesirable properties for a specific application and can include, forexample, electron-withdrawing groups, electron-donating groups, andsteric groups. When a molecule can have two or more substituents, thesubstituents can be joined together to form a ring such as a fused ringunless otherwise provided. Generally, the above groups and substituentsthereof can include those having up to 48 carbon atoms, typically 1 to36 carbon atoms and usually less than 24 carbon atoms, but greaternumbers are possible depending on the particular substituents selected.

The following is the description of the layer structure, materialselection, and fabrication process for OLED devices.

General OLED Device Architecture

The present invention can be employed in many OLED configurations usingsmall molecule materials, oligomeric materials, polymeric materials, orcombinations thereof. These include from very simple structures having asingle anode and cathode to more complex devices, such as passive matrixdisplays having orthogonal arrays of anodes and cathodes to form pixels,and active-matrix displays where each pixel is controlled independently,for example, with thin film transistors (TFTs). There are numerousconfigurations of the organic layers wherein the present invention issuccessfully practiced. For this invention, essential requirements are acathode, an anode, a LEL, an ETL, and a HIL.

One embodiment according to the present invention and especially usefulfor a small molecule device is shown in FIG. 1. OLED 100 contains asubstrate 110, an anode 120, a hole-injecting layer 130, ahole-transporting layer 132, a light-emitting layer 134, a hole-blockinglayer 135, an electron-transporting layer 136, an electron-injectinglayer 138 and a cathode 140. In some other embodiments, there areoptional spacer layers on either side of the LEL. These spacer layers donot typically contain light emissive materials. All of these layer typeswill be described in detail below. Note that the substrate canalternatively be located adjacent to the cathode, or the substrate canactually constitute the anode or cathode. Also, the total combinedthickness of the organic layers is preferably less than 500 nm.

The anode and cathode of the OLED are connected to a voltage/currentsource 150, through electrical conductors 160. Applying a potentialbetween the anode and cathode such that the anode is at a more positivepotential than the cathode operates the OLED. Holes are injected intothe organic EL element from the anode. Enhanced device stability cansometimes be achieved when the OLED is operated in an AC mode where, forsome time period in cycle, the potential bias is reversed and no currentflows. An example of an AC driven OLED is described in U.S. Pat. No.5,552,678.

Anode

When the desired EL emission is viewed through the anode, anode 120should be transparent or substantially transparent to the emission ofinterest. Common transparent anode materials used in this invention areindium-tin oxide (ITO), indium-zinc oxide (IZO), and tin oxide, butother metal oxides can work including, but not limited to, aluminum- orindium-doped zinc oxide, magnesium-indium oxide, and nickel-tungstenoxide. In addition to these oxides, metal nitrides, such as galliumnitride, and metal selenides, such as zinc selenide, and metal sulfides,such as zinc sulfide, can be used as the anode 120. For applicationswhere EL emission is viewed only through the cathode 140, thetransmissive characteristics of the anode 120 are immaterial and anyconductive material can be used, transparent, opaque or reflective.Example conductors for this application include, but are not limited to,gold, iridium, molybdenum, palladium, and platinum. Typical anodematerials, transmissive or otherwise, have a work function of 4.1 eV orgreater. Desired anode materials are commonly deposited by any suitableway such as evaporation, sputtering, chemical vapor deposition, orelectrochemical process. Anodes can be patterned using well-knownphotolithographic processes. Optionally, anodes can be polished prior toapplication of other layers to reduce surface roughness so as to reduceshort circuits or enhance reflectivity.

Hole Injection Layer

Although it is not always necessary, it is often useful to provide anHIL in the OLEDs. HIL 130 in the OLEDs can serve to facilitate holeinjection from the anode into the HTL, thereby reducing the drivevoltage of the OLEDs. Suitable materials for use in HIL 130 include, butare not limited to, porphyrinic compounds as described in U.S. Pat. No.4,720,432 and some aromatic amines, for example,4,4′,4″-tris[(3-ethylphenyl)phenylamino]triphenylamine (m-TDATA).Alternative hole-injecting materials reportedly useful in OLEDs aredescribed in EP Publication Numbers 0891121 and 1029909. Aromatictertiary amines discussed below can also be useful as hole-injectingmaterials. Other useful hole-injecting materials such asdipyrazino[2,3-f:2′,3′-h]quinoxalinehexacarbonitrile are described in USPatent Publication No. 2004/0113547 and U.S. Pat. No. 6,720,573. Inaddition, a p-type doped organic layer is also useful for the HIL asdescribed in U.S. Pat. No. 6,423,429. The term “p-type doped organiclayer” means that this layer has semiconducting properties after doping,and the electrical current through this layer is substantially carriedby the holes. The conductivity is provided by the formation of acharge-transfer complex as a result of hole transfer from the dopant tothe host material.

The thickness of the HIL 130 is in the range of from 0.1 nm to 200 nm,preferably, in the range of from 0.5 nm to 150 nm.

Hole Transport Layer

The HTL 132 contains at least one hole-transporting material such as anaromatic tertiary amine, where the latter is understood to be a compoundcontaining at least one trivalent nitrogen atom that is bonded only tocarbon atoms, at least one of which is a member of an aromatic ring. Inone form the aromatic tertiary amine is an arylamine, such as amonoarylamine, diarylamine, triarylamine, or a polymeric arylamine.Exemplary monomeric triarylamines are illustrated by Klupfel et al. U.S.Pat. No. 3,180,730. Other suitable triarylamines substituted with one ormore vinyl radicals or at least one active hydrogen-containing group aredisclosed by Brantley, et al. in U.S. Pat. Nos. 3,567,450 and 3,658,520.

A more preferred class of aromatic tertiary amines are those whichinclude at least two aromatic tertiary amine moieties as described inU.S. Pat. Nos. 4,720,432 and 5,061,569. Such compounds include thoserepresented by structural Formula (A)

wherein:

-   -   Q₁ and Q₂ are independently selected aromatic tertiary amine        moieties; and    -   G is a linking group such as an arylene, cycloalkylene, or        alkylene group of a carbon to carbon bond.

In one embodiment, at least one of Q₁ or Q₂ contains a polycyclic fusedring structure, e.g., a naphthalene. When G is an aryl group, it isconveniently a phenylene, biphenylene, or naphthalene moiety.

A useful class of triarylamines satisfying structural Formula A andcontaining two triarylamine moieties is represented by structuralFormula (B)

wherein:

-   -   R₁ and R₂ each independently represents a hydrogen atom, an aryl        group, or an alkyl group or R₁ and R₂ together represent the        atoms completing a cycloalkyl group; and    -   R₃ and R₄ each independently represents an aryl group, which is        in turn substituted with a diaryl substituted amino group, as        indicated by structural Formula (C)

wherein:

-   -   R₅ and R₆ are independently selected aryl groups. In one        embodiment, at least one of R₅ or R₆ contains a polycyclic fused        ring structure, e.g., a naphthalene.

Another class of aromatic tertiary amines are the tetraaryldiamines.Desirable tetraaryldiamines include two diarylamino groups, such asindicated by Formula (C), linked through an arylene group. Usefultetraaryldiamines include those represented by Formula (D)

wherein:

-   -   each ARE is an independently selected arylene group, such as a        phenylene or anthracene moiety;    -   n is an integer of from 1 to 4; and    -   Ar, R₇, R₈, and R₉ are independently selected aryl groups. In a        typical embodiment, at least one of Ar, R₇, R₈, and R₉ is a        polycyclic fused ring structure, e.g., a naphthalene.

Another class of the hole-transporting material comprises a material ofFormula (E):

-   -   In Formula (E), Ar₁-Ar₆ independently represent aromatic groups,        for example, phenyl groups or tolyl groups;    -   R₁-R₁₂ independently represent hydrogen or independently        selected substituent, for example an alkyl group containing from        1 to 4 carbon atoms, an aryl group, a substituted aryl group.

The various alkyl, alkylene, aryl, and arylene moieties of the foregoingstructural Formulae (A), (B), (C), (D), and (E) can each in turn besubstituted. Typical substituents include alkyl groups, alkoxy groups,aryl groups, aryloxy groups, and halogen such as fluoride, chloride, andbromide. The various alkyl and alkylene moieties typically contain fromabout 1 to 6 carbon atoms. The cycloalkyl moieties can contain from 3 toabout 10 carbon atoms, but typically contain five, six, or seven ringcarbon atoms, e.g. cyclopentyl, cyclohexyl, and cycloheptyl ringstructures. The aryl and arylene moieties are typically phenyl andphenylene moieties.

The HTL is formed of a single or a mixture of aromatic tertiary aminecompounds. Specifically, one can employ a triarylamine, such as atriarylamine satisfying the Formula (B), in combination with atetraaryldiamine, such as indicated by Formula (D). When a triarylamineis employed in combination with a tetraaryldiamine, the latter ispositioned as a layer interposed between the triarylamine and theelectron injecting and transporting layer. Aromatic tertiary amines areuseful as hole-injecting materials also. Illustrative of useful aromatictertiary amines are the following:

-   -   1,1-bis(4-di-p-tolylaminophenyl)cyclohexane;    -   1,1-bis(4-di-p-tolylaminophenyl)-4-phenylcyclohexane;    -   1,5-bis[N-(1-naphthyl)-N-phenylamino]naphthalene;    -   2,6-bis(di-p-tolylamino)naphthalene;    -   2,6-bis[di-(1-naphthyl)amino]naphthalene;    -   2,6-bis[N-(1-naphthyl)-N-(2-naphthyl)amino]naphthalene;    -   2,6-bis[N,N-di(2-naphthyl)amine]fluorene;    -   4-(di-p-tolylamino)-4′-[4(di-p-tolylamino)-styryl]stilbene;    -   4,4′-bis(diphenylamino)quadriphenyl;    -   4,4″-bis[N-(1-anthryl)-N-phenylamino]-p-terphenyl;    -   4,4′-bis[N-(1-coronenyl)-N-phenylamino]biphenyl;    -   4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB);    -   4,4′-bis[N-(1-naphthyl)-N-(2-naphthyl)amino]biphenyl (TNB);    -   4,4″-bis[N-(1-naphthyl)-N-phenylamino]p-terphenyl;    -   4,4′-bis[N-(2-naphthacenyl)-N-phenylamino]biphenyl;    -   4,4′-bis[N-(2-naphthyl)-N-phenylamino]biphenyl;    -   4,4′-bis[N-(2-perylenyl)-N-phenylamino]biphenyl;    -   4,4′-bis[N-(2-phenanthryl)-N-phenylamino]biphenyl;    -   4,4′-bis[N-(2-pyrenyl)-N-phenylamino]biphenyl;    -   4,4′-bis[N-(3-acenaphthenyl)-N-phenylamino]biphenyl;    -   4,4′-bis[N-(3-methylphenyl)-N-phenylamino]biphenyl (TPD);    -   4,4′-bis[N-(8-fluoranthenyl)-N-phenylamino]biphenyl;    -   4,4′-bis[N-(9-anthryl)-N-phenylamino]biphenyl;    -   4,4′-bis{N-phenyl-N-[4-(1-naphthyl)-phenyl]amino}biphenyl;    -   4,4′-bis[N-phenyl-N-(2-pyrenyl)amino]biphenyl;    -   4,4′,4″-tris[(3-methylphenyl)phenylamino]triphenylamine        (m-TDATA);    -   Bis(4-dimethylamino-2-methylphenyl)-phenylmethane;    -   N-phenylcarbazole;    -   N,N′-bis[4-([1,1′-biphenyl]-4-ylphenylamino)phenyl]-N,N′-di-1-naphthalenyl-[1,1′-biphenyl]-4,4′-diamine;    -   N,N′-bis[4-(di-1-naphthalenylamino)phenyl]-N,N′-di-1-naphthalenyl-[1,1′-biphenyl]-4,4′-diamine;    -   N,N′-bis[4-[(3-methylphenyl)phenylamino]phenyl]-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine;    -   N,N-bis[4-(diphenylamino)phenyl]-N′,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine;    -   N,N′-di-1-naphthalenyl-N,N′-bis[4-(1-naphthalenylphenylamino)phenyl]-[1,1′-biphenyl]-4,4′-diamine;    -   N,N′-di-1-naphthalenyl-N,N′-bis[4-(2-naphthalenylphenylamino)phenyl]-[1,1′-biphenyl]-4,4′-diamine;    -   N,N,N-tri(p-tolyl)amine;    -   N,N,N′,N′-tetra-p-tolyl-4-4′-diaminobiphenyl;    -   N,N,N′,N′-tetraphenyl-4,4′-diaminobiphenyl;    -   N,N,N′,N′-tetra-1-naphthyl-4,4′-diaminobiphenyl;    -   N,N,N′,N′-tetra-2-naphthyl-4,4′-diaminobiphenyl; and    -   N,N,N′,N′-tetra(2-naphthyl)-4,4″-diamino-p-terphenyl.

Another class of useful hole-transporting materials includes polycyclicaromatic compounds as described in EP Publication No. 1 009 041.Tertiary aromatic amines with more than two amine groups can be usedincluding oligomeric materials. In addition, polymeric hole-transportingmaterials are used such as poly(N-vinylcarbazole) (PVK), polythiophenes,polypyrrole, polyaniline, and copolymers such aspoly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) also calledPEDOT/PSS.

The thickness of the HTL 132 is in the range of from 5 nm to 200 nm,preferably, in the range of from 10 nm to 150 nm.

Exciton Blocking Layer (EBL)

An optional exciton- or electron-blocking layer can be present betweenthe HTL and the LEL (not shown in FIG. 1). Some suitable examples ofsuch blocking layers are described in US Publication No. 2006/0134460.

Light Emitting Layer

As more fully described in U.S. Pat. No. 4,769,292 and 5,935,721, thelight-emitting layer(s) (LEL) 134 of the organic EL element shown inFIG. 1 comprises a luminescent, fluorescent or phosphorescent materialwhere electroluminescence is produced as a result of electron-hole pairrecombination in this region. The light-emitting layer can be comprisedof a single material, but more commonly consists ofnon-electroluminescent compounds (generally referred to as the host)doped with an electroluminescent guest compound (generally referred toas the dopant) or compounds where light emission comes primarily fromthe electroluminescent compound and can be of any color.Electroluminescent compounds can be coated as 0.01 to 50% into thenon-electroluminescent component material, but typically coated as 0.01to 30% and more typically coated as 0.01 to 15% into thenon-electroluminescent component. The thickness of the LEL can be anysuitable thickness. It can be in the range of from 0.1 mm to 100 mm.

An important relationship for choosing a dye as a electroluminescentcomponent is a comparison of the bandgap potential which is defined asthe energy difference between the highest occupied molecular orbital andthe lowest unoccupied molecular orbital of the molecule. For efficientenergy transfer from the non-electroluminescent compound to theelectroluminescent compound molecule, a necessary condition is that theband gap of the electroluminescent compound is smaller than that of thenon-electroluminescent compound or compounds. Thus, the selection of anappropriate host material is based on its electronic characteristicsrelative to the electronic characteristics of the electroluminescentcompound, which itself is chosen for the nature and efficiency of thelight emitted. As described below, fluorescent and phosphorescentdopants typically have different electronic characteristics so that themost appropriate hosts for each can be different. However in some cases,the same host material can be useful for either type of dopant.

Non-electroluminescent compounds and emitting molecules known to be ofuse include, but are not limited to, those disclosed in U.S. Pat. Nos.5,141,671; 5,150,006; 5,151,629; 5,405,709; 5,484,922; 5,593,788;5,645,948; 5,683,823; 5,755,999; 5,928,802; 5,935,720; 5,935,721; and6,020,078.

a) Phosphorescent Light Emitting Layers

Suitable hosts for phosphorescent LELs should be selected so thattransfer of a triplet exciton can occur efficiently from the host to thephosphorescent dopant(s) but cannot occur efficiently from thephosphorescent dopant(s) to the host. Therefore, it is highly desirablethat the triplet energy of the host be higher than the triplet energiesof phosphorescent dopant. Generally speaking, a large triplet energyimplies a large optical band gap. However, the band gap of the hostshould not be chosen so large as to cause an unacceptable barrier toinjection of holes into the fluorescent blue LEL and an unacceptableincrease in the drive voltage of the OLED. The host in a phosphorescentLEL can include any of the aforementioned hole-transporting materialused for the HTL 132, as long as it has a triplet energy higher thanthat of the phosphorescent dopant in the layer. The host used in aphosphorescent LEL can be the same as or different from thehole-transporting material used in the HTL 132. In some cases, the hostin the phosphorescent LEL can also suitably include anelectron-transporting material (it will be discussed thereafter), aslong as it has a triplet energy higher than that of the phosphorescentdopant.

In addition to the aforementioned hole-transporting materials in the HTL132, there are several other classes of hole-transporting materialssuitable for use as the host in a phosphorescent LEL.

One desirable host comprises a hole-transporting material of Formula(F):

-   -   In Formula (F), R₁ and R₂ represent substituents, provided that        R₁ and R₂ can join to form a ring. For example, R₁ and R₂ can be        methyl groups or join to form a cyclohexyl ring;    -   Ar₁-Ar₄ represent independently selected aromatic groups, for        example phenyl groups or tolyl groups; and    -   R₃-R₁₀ independently represent hydrogen, alkyl, substituted        alkyl, aryl, substituted aryl group.

Examples of suitable materials include, but are not limited to:

-   -   1,1-Bis(4-(N,N-di-p-tolylamino)phenyl)cyclohexane (TAPC);    -   1,1-Bis(4-(N,N-di-p-tolylamino)phenyl)cyclopentane;    -   4,4′-(9H-fluoren-9-ylidene)bis[N,N-bis(4-methylphenyl)-benzenamine;    -   1,1-Bis(4-(N,N-di-p-tolylamino)phenyl)-4-phenylcyclohexane;    -   1,1-Bis(4-(N,N-di-p-tolylamino)phenyl)-4-methylcyclohexane;    -   1,1-Bis(4-(N,N-di-p-tolylamino)phenyl)-3-phenylpropane;    -   Bis[4-(N,N-diethylamino)-2-methylphenyl](4-methylpenyl)methane;    -   Bis[4-(N,N-diethylamino)-2-methylphenyl](4-methylphenyl)ethane;    -   4-(4-Diethylaminophenyl)triphenylmethane;    -   4,4′-Bis(4-diethylaminophenyl)diphenylmethane.    -   A useful class of triarylamines suitable for use as the host        includes carbazole derivatives such as those represented by        Formula (G):

-   -   In Formula (G), Q independently represents nitrogen, carbon, an        aryl group, or substituted aryl group, preferably a phenyl        group;    -   R₁ is preferably an aryl or substituted aryl group, and more        preferably a phenyl group, substituted phenyl, biphenyl,        substituted biphenyl group;    -   R₂ through R₇ are independently hydrogen, alkyl, phenyl or        substituted phenyl group, aryl amine, carbazole, or substituted        carbazole;    -   and n is selected from 1 to 4.

Another useful class of carbazoles satisfying structural Formula (G) isrepresented by Formula (H):

wherein:

-   -   n is an integer from 1 to 4;    -   Q is nitrogen, carbon, an aryl, or substituted aryl;    -   R₂ through R₇ are independently hydrogen, an alkyl group, phenyl        or substituted phenyl, an aryl amine, a carbazole and        substituted carbazole.

Illustrative of useful substituted carbazoles are the following:

-   -   4-(9H-carbazol-9-yl)-N,N-bis[4-(9H-carbazol-9-yl)phenyl]-benzenamine        (TCTA);    -   4-(3-phenyl-9H-carbazol-9-yl)-N,N-bis[4(3-phenyl-9H-carbazol-9-yl)phenyl]-benzenamine;    -   9,9′-[5′-[4-(9H-carbazol-9-yl)phenyl][1,1′:3′,1″-terphenyl]-4,4″-diyl]bis-9H-carbazole.    -   9,9′-(2,2′-dimethyl[1,1′-biphenyl]-4,4′-diyl)bis-9H-carbazole        (CDBP);    -   9,9′-[1,1′-biphenyl]-4,4′-diylbis-9H-carbazole (CBP);    -   9,9′-(1,3-phenylene)bis-9H-carbazole (mCP);    -   9,9′-(1,4-phenylene)bis-9H-carbazole;    -   9,9′,9″-(1,3,5-benzenetriyl)tris-9H-carbazole;    -   9,9′-(1,4-phenylene)bis[N,N,N′,N′-tetraphenyl-9H-carbazole-3,6-diamine;    -   9-[4-(9H-carbazol-9-yl)phenyl]-N,N-diphenyl-9H-carbazol-3-amine;    -   9,9′-(1,4-phenylene)bis[N,N-diphenyl-9H-carbazol-3-amine;    -   9-[4-(9H-carbazol-9-yl)phenyl]-N,N,N′,N′-tetraphenyl-9H-carbazole-3,6-diamine.

The above classes of hosts suitable for phosphorescent LELs can also beused as hosts in fluorescent LELs as well.

Suitable phosphorescent dopants for use in a phosphorescent LEL can beselected from the phosphorescent materials described by Formula (J)below:

wherein:

-   -   A is a substituted or unsubstituted heterocyclic ring containing        at least one nitrogen atom;    -   B is a substituted or unsubstituted aromatic or heteroaromatic        ring, or ring containing a vinyl carbon bonded to M;    -   X—Y is an anionic bidentate ligand;    -   m is an integer from 1 to 3; and    -   n in an integer from 0 to 2 such that m+n=3 for M═Rh or Ir; or    -   m is an integer from 1 to 2 and n in an integer from 0 to 1 such        that m+n=2 for M═Pt or Pd.

Compounds according to Formula (J) can be referred to as C,N- (orC^N-)cyclometallated complexes to indicate that the central metal atomis contained in a cyclic unit formed by bonding the metal atom to carbonand nitrogen atoms of one or more ligands. Examples of heterocyclic ringA in Formula (J) include substituted or unsubstituted pyridine,quinoline, isoquinoline, pyrimidine, indole, indazole, thiazole, andoxazole rings. Examples of ring B in Formula (J) include substituted orunsubstituted phenyl, napthyl, thienyl, benzothienyl, furanyl rings.Ring B in Formula (J) can also be a N-containing ring such as pyridine,with the proviso that the N-containing ring bonds to M through a C atomas shown in Formula (J) and not the N atom.

An example of a tris-C,N-cyclometallated complex according to formula(J) with m=3 and n=0 is tris(2-phenyl-pyridinato-N,C^(2′)-)Iridium(III), shown below in stereodiagrams as facial (fac-) or meridional(mer-) isomers.

Generally, facial isomers are preferred since they are often found tohave higher phosphorescent quantum yields than the meridional isomers.Additional examples of tris-C,N-cyclometallated phosphorescent materialsaccording to formula (J) aretris(2-(4′-methylphenyl)pyridinato-N,C^(2′))Iridium(III),tris(3-phenylisoquinolinato-N,C^(2′))Iridium(III),tris(2-phenylquinolinato-N,C^(2′))Iridium(III),tris(1-phenylisoquinolinato-N,C^(2′))Iridium(III),tris(1-(4′-methylphenyl)isoquinolinato-N,C^(2′))Iridium(III),tris(2-(4′,6′-diflourophenyl)-pyridinato-N,C^(2′))Iridium(III),tris(2-((5′-phenyl)-phenyl)pyridinato-N,C^(2′))Iridium(III),tris(2-(2′-benzothienyl)pyridinato-N,C^(3′))Iridium(III),tris(2-phenyl-3,3′dimethyl)indolato-N,C^(2′))Ir(III),tris(1-phenyl-1H-indazolato-N,C^(2′))Ir(III).

Of these, tris(1-phenylisoquinoline) iridium (III) (also referred to asIr(piq)₃) and tris(2-phenylpyridine) iridium (also referred to asIr(ppy)₃) are particularly suitable for this invention.

Tris-C,N-cyclometallated phosphorescent materials also include compoundsaccording to Formula (J) wherein the monoanionic bidentate ligand X—Y isanother C,N-cyclometallating ligand. Examples includebis(1-phenylisoquinolinato-N,C^(2′))(2-phenylpyridinato-N,C^(2′))Iridium(III)andbis(2-phenylpyridinato-N,C^(2′))(1-phenylisoquinolinato-N,C^(2′))Iridium(III).Synthesis of such tris-C,N-cyclometallated complexes containing twodifferent C,N-cyclometalling ligands can be conveniently synthesized bythe following steps. First, a bis-C,N-cyclometallated diiridium dihalidecomplex (or analogous dirhodium complex) is made according to the methodof Nonoyama (Bull. Chem. Soc. Jpn., 47, 767 (1974)). Secondly, a zinccomplex of the second, dissimilar C,N-cyclometallating ligand isprepared by reaction of a zinc halide with a lithium complex or Grignardreagent of the cyclometallating ligand. Third, the thus formed zinccomplex of the second C,N-cyclometallating ligand is reacted with thepreviously obtained bis-C,N-cyclometallated diiridium dihalide complexto form a tris-C,N-cyclometallated complex containing the two differentC,N-cyclometallating ligands. Desirably, the thus obtainedtris-C,N-cyclometallated complex containing the two differentC,N-cyclometallating ligands can be converted to an isomer wherein the Catoms bonded to the metal (e.g. Ir) are all mutually cis by heating in asuitable solvent such as dimethyl sulfoxide.

Suitable phosphorescent materials according to formula (J) can inaddition to the C,N-cyclometallating ligand(s) also contain monoanionicbidentate ligand(s) X—Y that are not C,N-cyclometallating. Commonexamples are beta-diketonates such as acetylacetonate, and Schiff basessuch as picolinate. Examples of such mixed ligand complexes according toformula (J) includebis(2-phenylpyridinato-N,C^(2′))Iridium(II)(acetylacetonate),bis(2-(2′-benzothienyl)pyridinato-N,C^(3′))Iridium(III)(acetylacetonate),andbis(2-(4′,6′-diflourophenyl)-pyridinato-N,C^(2′))Iridium(III)(picolinate).

Other important phosphorescent materials according to formula (J)include C,N-cyclometallated Pt(II) complexes such ascis-bis(2-phenylpyridinato-N,C^(2′))platinum(II),cis-bis(2-(2′-thienyl)pyridinato-N,C^(3′))platinum(II),cis-bis(2-(2′-thienyl)quinolinato-N,C^(5′))platinum(II), or(2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′))platinum(II)(acetylacetonate).

The emission wavelengths (color) of C,N-cyclometallated phosphorescentmaterials according to Formula (J) are governed principally by thelowest energy optical transition of the complex and hence by the choiceof the C,N-cyclometallating ligand. For example,2-phenyl-pyridinato-N,C²′ complexes are typically green emissive while1-phenyl-isoquinolinolato-N,C²′ complexes are typically red emissive. Inthe case of complexes having more than one C,N-cyclometallating ligand,the emission will be that of the ligand having the property of longestwavelength emission. Emission wavelengths can be further shifted by theeffects of substituent groups on the C,N-cyclometallating ligands. Forexample, substitution of electron donating groups at appropriatepositions on the N-containing ring A or electron accepting groups on theC-containing ring B tend to blue-shift the emission relative to theunsubstituted C,N-cyclometallated ligand complex. Selecting amonodentate anionic ligand X,Y in formula (J) having more electronaccepting properties also tends to blue-shift the emission of aC,N-cyclometallated ligand complex. Examples of complexes having bothmonoanionic bidentate ligands possessing electron accepting propertiesand electron accepting substituent groups on the C-containing ring Bincludebis(2-(4′,6′-difluorophenyl)-pyridinato-N,C^(2′))iridium(III)(picolinate)andbis(2-(4′,6′-difluorophenyl)-pyridinato-N,C^(2′))iridium(III)(tetrakis(1-pyrazolyl)borate).

The central metal atom in phosphorescent materials according to formula(J) can be Rh or Ir (m+n=3) and Pd or Pt (m+n=2). Preferred metal atomsare Ir and Pt since they tend to give higher phosphorescent quantumefficiencies according to the stronger spin-orbit coupling interactionsgenerally obtained with elements in the third transition series.

In addition to bidentate C,N-cyclometallating complexes represented byFormula (J), many suitable phosphorescent materials contain multidentateC,N-cyclometallating ligands. Phosphorescent materials having tridentateligands suitable for use in the present invention are disclosed in U.S.Pat. No. 6,824,895 and references therein, incorporated in theirentirety herein by reference. Phosphorescent materials havingtetradentate ligands suitable for use in the present invention aredescribed by the following formulae:

wherein:

-   -   M is Pt or Pd;    -   R¹-R⁷ represent hydrogen or independently selected substituents,        provided that R¹ and R², R² and R³, R³ and R⁴, R⁴ and R⁵, R⁵ and        R⁶, as well as R⁶ and R⁷ can join to form a ring group;    -   R⁸-R¹⁴ represent hydrogen or independently selected        substituents, provided that R⁸ and R⁹, R⁹ and R¹⁰, R¹⁰ and R¹¹,        R¹¹ and R¹², R¹² and R¹³, as well as R¹³ and R¹⁴, can join to        form a ring group;    -   E represents a bridging group selected from the following:

wherein:

-   -   R and R′ represent hydrogen or independently selected        substituents; provided R and R′ can combine to form a ring        group.

One desirable tetradentate C,N-cyclometallated phosphorescent materialsuitable for use in as the phosphorescent dopant is represented by thefollowing formula:

wherein:

-   -   R¹-R⁷ represent hydrogen or independently selected substituents,        provided that R¹ and R², R² and R³, R³ and R⁴, R⁴ and R⁵, R⁵ and        R⁶, as well as R⁶ and R⁷ can combine to form a ring group;    -   R⁸-R¹⁴ represent hydrogen or independently selected        substituents, provided that R⁸ and R⁹, R⁹ and R¹⁰, R¹⁰ and R¹¹,        R¹¹ and R¹², R¹² and R¹³, as well as R¹³ and R¹⁴ can combine to        form a ring group; and    -   Z¹-Z⁵ represent hydrogen or independently selected substituents,        provided that Z¹ and Z², Z² and Z³, Z³ and Z⁴, as well as Z⁴ and        Z⁵ can combine to form a ring group.

Specific examples of phosphorescent materials having tetradentateC,N-cyclometallating ligands suitable for use in the present inventioninclude compounds (M-1), (M-2) and (M-3) represented below.

Phosphorescent materials having tetradentate C,N-cyclometallatingligands can be synthesized by reacting the tetradentateC,N-cyclometallating ligand with a salt of the desired metal, such asK₂PtCl₄, in a proper organic solvent such as glacial acetic acid to formthe phosphorescent material having tetradentate C,N-cyclometallatingligands. A tetraalkylammonium salt such as tetrabutylammonium chloridecan be used as a phase transfer catalyst to accelerate the reaction.

Other phosphorescent materials that do not involve C,N-cyclometallatingligands are known. Phosphorescent complexes of Pt(II), Ir(I), and Rh(I)with maleonitriledithiolate have been reported (Johnson et al., J. AmChem. Soc., 105, 1795 (1983)). Re(I) tricarbonyl diimine complexes arealso known to be highly phosphorescent (Wrighton and Morse, J. Am. Chem.Soc., 96, 998 (1974); Stufkens, Comments Inorg. Chem., 13, 359 (1992);Yam, Chem. Commun., 789 (2001)). Os(II) complexes containing acombination of ligands including cyano ligands and bipyridyl orphenanthroline ligands have also been demonstrated in a polymer OLED (Maet al., Synthetic Metals, 94, 245 (1998)).

Porphyrin complexes such as 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine platinum(II) are also useful phosphorescent dopant.

Still other examples of useful phosphorescent materials includecoordination complexes of the trivalent lanthanides such as Tb³⁺ andEu³⁺ (Kido et al., Chem. Lett., 657 (1990); J. Alloys and Compounds,192, 30 (1993); Jpn. J. Appl. Phys., 35, L394 (1996) and Appl. Phys.Lett., 65, 2124 (1994)).

The phosphorescent dopant in a phosphorescent LEL is typically presentin an amount of from 1 to 20% by volume of the LEL, and convenientlyfrom 2 to 8% by volume of the LEL. In some embodiments, thephosphorescent dopant(s) can be attached to one or more host materials.The host materials can further be polymers. The phosphorescent dopant inthe first phosphorescent light-emitting layer is selected from green andred phosphorescent materials.

The thickness of a phosphorescent LEL is greater than 0.5 nm,preferably, in the range of from 1.0 nm to 40 nm.

b) Fluorescent Light Emitting Layers

Although the term “fluorescent” is commonly used to describe anylight-emitting material, in this case it refers to a material that emitslight from a singlet excited state. Fluorescent materials can be used inthe same layer as the phosphorescent material, in adjacent layers, inadjacent pixels, or any combination. Care must be taken not to selectmaterials that will adversely affect the performance of thephosphorescent materials of this invention. One skilled in the art willunderstand that concentrations and triplet energies of materials in thesame layer as the phosphorescent material or in an adjacent layer mustbe appropriately set so as to prevent unwanted quenching of thephosphorescence.

Typically, a fluorescent LEL includes at least one host and at least onefluorescent dopant. The host can be a hole-transporting material or anyof the suitable hosts for phosphorescent dopants as defined above or canbe an electron-transporting material as defined below.

The dopant is typically chosen from highly fluorescent dyes, e.g.,transition metal complexes as described in WO Publication Numbers98/55561, 00/18851, 00/57676, and 00/70655.

Useful fluorescent dopants include, but are not limited to, derivativesof anthracene, tetracene, xanthene, perylene, phenylene,dicyanomethylenepyran compounds, thiopyran compounds, polymethinecompounds, pyrylium and thiapyrylium compounds, arylpyrene compounds,arylenevinylene compounds, periflanthene derivatives, indenoperylenederivatives, bis(azinyl)amine boron compounds, bis(azinyl)methane boroncompounds, distryrylbenzene derivatives, distyrylbiphenyl derivatives,distyrylamine derivatives, and carbostyryl compounds.

Some fluorescent emitting materials include, but are not limited to,derivatives of anthracene, tetracene, xanthene, perylene, rubrene,coumarin, rhodamine, and quinacridone, dicyanomethylenepyran compounds,thiopyran compounds, polymethine compounds, pyrylium and thiapyryliumcompounds, fluorene derivatives, periflanthene derivatives,indenoperylene derivatives, bis(azinyl)amine boron compounds,bis(azinyl)methane compounds (as described in U.S. Pat. No. 5,121,029)and carbostyryl compounds. Illustrative examples of useful materialsinclude, but are not limited to, the following:

X R1 R2 FD-9 O H H FD-10 O H Methyl FD-11 O Methyl H FD-12 O MethylMethyl FD-13 O H t-butyl FD-14 O t-butyl H FD-15 O t-butyl t-butyl FD-16S H H FD-17 S H Methyl FD-18 S Methyl H FD-19 S Methyl Methyl FD-20 S Ht-butyl FD-21 S t-butyl H FD-22 S t-butyl t-butyl

X R1 R2 FD-13 O H H FD-24 O H Methyl FD-25 O Methyl H FD-26 O MethylMethyl FD-27 O H t-butyl FD-28 O t-butyl H FD-29 O t-butyl t-butyl FD-30S H H FD-31 S H Methyl FD-32 S Methyl H FD-33 S Methyl Methyl FD-34 S Ht-butyl FD-35 S t-butyl H FD-36 S t-butyl t-butyl

R FD-37 phenyl FD-38 methyl FD-39 t-butyl FD-40 mesityl

R FD-41 phenyl FD-42 methyl FD-43 t-butyl FD-44 mesityl

Preferred fluorescent blue dopants can be found in Chen, Shi, and Tang,“Recent Developments in Molecular Organic Electroluminescent Materials,”Macromol. Symp. 125, 1 (1997) and the references cited therein; Hung andChen, “Recent Progress of Molecular Organic Electroluminescent Materialsand Devices,” Mat. Sci. and Eng. R39, 143 (2002) and the referencescited therein.

A particularly preferred class of blue-emitting fluorescent dopants isrepresented by Formula (N), known as a bis(azinyloamine borane complex,and is described in U.S. Pat. No. 6,661,023.

wherein:

-   -   A and A′ represent independent azine ring systems corresponding        to 6-membered aromatic ring systems containing at least one        nitrogen;    -   each X^(a) and X^(b) is an independently selected substituent,        two of which can join to form a fused ring to A or A′;    -   m and n are independently 0 to 4;    -   Z^(a) and Z^(b) are independently selected substituents; and    -   1, 2, 3, 4, 1′, 2′, 3′, and 4′ are independently selected as        either carbon or nitrogen atoms.

Desirably, the azine rings are either quinolinyl or isoquinolinyl ringssuch that 1, 2, 3, 4, 1′, 2′, 3′, and 4′ are all carbon; m and n areequal to or greater than 2; and X^(a) and X^(b) represent at least twocarbon substituents which join to form an aromatic ring. Desirably,Z^(a) and Z^(b) are fluorine atoms.

Preferred embodiments further include devices where the two fused ringsystems are quinoline or isoquinoline systems; the aryl or heterocyclicsubstituent is a phenyl group; there are present at least two X^(a)groups and two X^(b) groups which join to form a 6-6 fused ring, thefused ring systems are fused at the 1-2, 3-4, 1′-2′, or 3′-4′ positions,respectively; one or both of the fused rings is substituted by a phenylgroup; and where the dopant is depicted in Formulae (N-a), (N-b), or(N-c).

wherein:

-   -   each X^(c), X^(d), X^(e), X^(f), X^(g), and X^(h) is hydrogen or        an independently selected substituent, one of which must be an        aryl or heterocyclic group.

Desirably, the azine rings are either quinolinyl or isoquinolinyl ringssuch that 1, 2, 3, 4, 1′, 2′, 3′, and 4′ are all carbon; m and n areequal to or greater than 2; and X^(a) and X^(b) represent at least twocarbon substituents which join to form an aromatic ring, and one is anaryl or substituted aryl group. Desirably, Z^(a) and Z^(b) are fluorineatoms.

Of these, compound FD-54 is particularly useful.

Coumarins represent a useful class of green-emitting dopants asdescribed by Tang et al. in U.S. Pat. Nos. 4,769,292 and 6,020,078.Green dopants or light-emitting materials can be coated as 0.01 to 50%by weight into the host material, but typically coated as 0.01 to 30%and more typically coated as 0.01 to 15% by weight into the hostmaterial. Examples of useful green-emitting coumarins include C545T andC545TB. Quinacridones represent another useful class of green-emittingdopants. Useful quinacridones are described in U.S. Pat. No. 5,593,788,JP Publication No. 09-13026A, and commonly assigned U.S. patentapplication Ser. No. 10/184,356, filed Jun. 27, 2002 by LeliaCosimbescu, entitled “DEVICE CONTAINING GREEN ORGANIC LIGHT-EMITTINGDIODE,” the disclosure of which is incorporated herein.

Examples of particularly useful green-emitting quinacridones are FD-7and FD-8.

Formula (N-d) below represents another class of green-emitting dopantsuseful in the invention.

wherein:

-   -   A and A′ represent independent azine ring systems corresponding        to 6-membered aromatic ring systems containing at least one        nitrogen;    -   each X^(a) and X^(b) is an independently selected substituent,        two of which can join to form a fused ring to A or A′;    -   m and n are independently 0 to 4;    -   Y is H or a substituent;    -   Z^(a) and Z^(b) are independently selected substituents; and    -   1, 2, 3, 4, 1′, 2′, 3′, and 4′ are independently selected as        either carbon or nitrogen atoms.

In the device, 1, 2, 3, 4, 1′, 2′, 3′, and 4′ are conveniently allcarbon atoms. The device can desirably contain at least one or both ofring A or A′ that contains substituents joined to form a fused ring. Inone useful embodiment, there is present at least one X^(a) or X^(b)group selected from the group consisting of halide and alkyl, aryl,alkoxy, and aryloxy groups. In another embodiment, there is present aZ^(a) and Z^(b) group independently selected from the group consistingof fluorine and alkyl, aryl, alkoxy and aryloxy groups. A desirableembodiment is where Z^(a) and Z^(b) are F. Y is suitably hydrogen or asubstituent such as an alkyl, aryl, or heterocyclic group.

The emission wavelength of these compounds can be adjusted to someextent by appropriate substitution around the central bis(azinyl)metheneboron group to meet a color aim, namely green. Some examples of usefulmaterial are FD-50, FD-51, and FD-52.

Naphthacenes and derivatives thereof also represent a useful class ofemitting dopants, which can also be used as stabilizers. These dopantmaterials can be coated as 0.01 to 50% by weight into the host material,but typically coated as 0.01 to 30% and more typically coated as 0.01 to15% by weight into the host material. Naphthacene derivative YD-1(t-BuDPN) below, is an example of a dopant material used as astabilizer.

Some examples of this class of materials are also suitable as hostmaterials as well as dopants. For example, see U.S. Pat. Nos. 6,773,832or 6,720,092. A specific example of this would be rubrene (FD-5).

Another class of useful dopants are perylene derivatives; for examplesee U.S. Pat. No. 6,689,493. A specific examples is FD-46.

Metal complexes of 8-hydroxyquinoline and similar derivatives (FormulaO) constitute one class of useful non-electroluminescent host compoundscapable of supporting electroluminescence, and are particularly suitablefor light emission of wavelengths longer than 500 nm, e.g., green,yellow, orange, and red.

wherein:

-   -   M represents a metal;    -   n is an integer of from 1 to 4; and    -   Z independently in each occurrence represents the atoms        completing a nucleus having at least two fused aromatic rings.

From the foregoing it is apparent that the metal can be monovalent,divalent, trivalent, or tetravalent metal. The metal can, for example,be an alkali metal, such as lithium, sodium, or potassium; an alkalineearth metal, such as magnesium or calcium; an earth metal, such asaluminum or gallium, or a transition metal such as zinc or zirconium.Generally any monovalent, divalent, trivalent, or tetravalent metalknown to be a useful chelating metal can be employed.

Z completes a heterocyclic nucleus containing at least two fusedaromatic rings, at least one of which is an azole or azine ring.Additional rings, including both aliphatic and aromatic rings, can befused with the two required rings, if required. To avoid addingmolecular bulk without improving on function the number of ring atoms isusually maintained at 18 or less.

Illustrative of useful chelated oxinoid compounds are the following:

-   -   O-1: Aluminum trisoxine[alias,        tris(8-quinolinolato)aluminum(III)]    -   O-2: Magnesium bisoxine[alias,        bis(8-quinolinolato)magnesium(II)]    -   O-3: Bis[benzo{f}-8-quinolinolato]zinc(II)    -   O-4:        Bis(2-methyl-8-quinolinolato)aluminum(III)-μ-oxo-bis(2-methyl-8-quinolinolato)aluminum(III)    -   O-5: Indium trisoxine[alias, tris(8-quinolinolato)indium]    -   O-6: Aluminum tris(5-methyloxine)[alias,        tris(5-methyl-8-quinolinolato) aluminum(III)]    -   O-7: Lithium oxine[alias, (8-quinolinolato)lithium(I)]    -   O-8: Gallium oxine[alias, tris(8-quinolinolato)gallium(III)]    -   O-9: Zirconium oxine[alias, tetra(8-quinolinolato)zirconium(IV)]    -   O-10: Bis(2-methyl-8-quinolinato)-4-phenylphenolatoaluminum(III)    -   Anthracene derivatives according to formula (P) are also useful        host materials in the LEL:

wherein:

-   -   R₁-R₁₀ are independently chosen from hydrogen, alkyl groups from        1-24 carbon atoms or aromatic groups from 6-24 carbon atoms.        Particularly preferred are compounds where R₁ and R₆ are phenyl,        biphenyl or napthyl, R₃ is phenyl, substituted phenyl or napthyl        and R₂, R₄, R₅, R₇-R₁₀ are all hydrogen. Such anthracene hosts        are known to have excellent electron transporting properties.

Particularly desirable are derivatives of9,10-di-(2-naphthyl)anthracene. Illustrative examples include9,10-di-(2-naphthyl)anthracene (ADN) and2-t-butyl-9,10-di-(2-naphthyl)anthracene (TBADN). Other anthracenederivatives can be useful as an non-electroluminescent compound in theLEL, such as diphenylanthracene and its derivatives, as described inU.S. Pat. No. 5,927,247. Styrylarylene derivatives as described in U.S.Pat. No. 5,121,029 and JP Publication No. 08333569 are also usefulnon-electroluminescent materials. For example,9,10-bis[4-(2,2-diphenylethenyl)phenyl]anthracene,4,4′-Bis(2,2-diphenylethenyl)-1,1′-biphenyl (DPVBi) and phenylanthracenederivatives as described in EP Patent No. 681,019 are usefulnon-electroluminescent materials.

Some illustrative examples of suitable anthracenes are:

Spacer Layer

Spacer layers, when present, are located in direct contact to a LEL.They can be located on either the anode or cathode, or even both sidesof the LEL. They typically do not contain any light-emissive dopants.One or more materials can be used and could be either ahole-transporting material as defined above or an electron-transportingmaterial as defined below. If located next to a phosphorescent LEL, thematerial in the spacer layer should have higher triplet energy than thatof the phosphorescent dopant in the LEL. Most desirably, the material inthe spacer layer will be the same as used as the host in the adjacentLEL. Thus, any of the host materials described as also suitable for usein a spacer layer. The spacer layer should be thin; at least 0.1 nm, butpreferably in the range of from 1.0 nm to 20 nm.

Hole-Blocking Layer (HBL)

When a LEL containing a phosphorescent emitter is present, it isdesirable to locate a hole-blocking layer 135 between theelectron-transporting layer 136 and the light-emitting layer 134 to helpconfine the excitons and recombination events to the LEL. In this case,there should be an energy barrier for hole migration from co-hosts intothe hole-blocking layer, while electrons should pass readily from thehole-blocking layer into the light-emitting layer comprising co-hostmaterials and a phosphorescent emitter. It is further desirable that thetriplet energy of the hole-blocking material be greater than that of thephosphorescent material. Suitable hole-blocking materials are describedin WO Publication Numbers 00/70655, 01/41512, and 01/93642. Two examplesof useful hole-blocking materials are bathocuproine (BCP) andbis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III) (BAlq).Metal complexes other than BAlq are also known to block holes andexcitons as described in US Publication No. 2003/0068528. When ahole-blocking layer is used, its thickness can be between 2 and 100 nmand suitably between 5 and 10 nm.

Electron Transporting Layer

In some embodiments, the electron-transporting layer 136 can contain thefluoranthene compound or can contain a mixture of the fluoranthenecompound with other appropriate materials. As described previously, inone desirable embodiment, the electron-transporting layer includespolycyclic aromatic compound such as a fluoranthene derivative or a9,10-diarylanthracene derivative. In particular, fluoranthenehydrocarbon derivatives with aromatic groups in the 7,10-positions areespecially desirable. In further embodiments, the ETL can contain both afluoranthene compound and a polycyclic aromatic compound. In someembodiments, the ETL also contains at least one material chosen fromalkali metals, alkali metal compounds, alkaline earth metals, oralkaline earth metal compounds, or combinations thereof.

In addition to any of the electron-transporting materials previouslydescribed, any other materials known to be suitable for use in the ETLcan be used. Included are, but are not limited to, chelated oxinoidcompounds, anthracene derivatives, pyridine-based materials, imidazoles,oxazoles, thiazoles and their derivatives, polybenzobisazoles,cyano-containing polymers and perfluorinated materials. Otherelectron-transporting materials include various butadiene derivatives asdisclosed in U.S. Pat. No. 4,356,429 and various heterocyclic opticalbrighteners as described in U.S. Pat. No. 4,539,507.

A preferred class of benzazoles is described by Shi et al. in U.S. Pat.Nos. 5,645,948 and 5,766,779. Such compounds are represented bystructural Formula (Q):

-   -   In formula (Q), n is selected from 2 to 8 and i is selected from        1-5;    -   Z is independently O, NR or S;    -   R is individually hydrogen; alkyl of from 1 to 24 carbon atoms,        for example, propyl, t-butyl, heptyl, and the like; aryl or        hetero-atom substituted aryl of from 5 to 20 carbon atoms, for        example, phenyl and naphthyl, furyl, thienyl, pyridyl,        quinolinyl and other heterocyclic systems; or halo such as        chloro, fluoro; or atoms necessary to complete a fused aromatic        ring; and    -   X is a linkage unit including carbon, alkyl, aryl, substituted        alkyl, or substituted aryl, which conjugately or unconjugately        connects the multiple benzazoles together.

An example of a useful benzazole is2,2′,2″-(1,3,5-phenylene)tris[1-phenyl-1H-benzimidazole] (TPBI)represented by a formula (Q-1) shown below:

Another suitable class of the electron-transporting materials includesvarious substituted phenanthrolines as represented by Formula (R).

In Formula (R), R₁-R₈ are independently hydrogen, alkyl group, aryl orsubstituted aryl group, and at least one of R₁-R₈ is aryl group orsubstituted aryl group.

Specific examples of the phenanthrolines useful in the EIL are2,9-dimethyl-4,7-diphenyl-phenanthroline (BCP) (see formula (R-1)) and4,7-diphenyl-1,10-phenanthroline (Bphen) (see formula (R-2)).

Suitable triarylboranes that function as an electron-transportingmaterial can be selected from compounds having the chemical Formula (S):

wherein:

-   -   Ar₁ to Ar₃ are independently an aromatic hydrocarbocyclic group        or an aromatic heterocyclic group which can have a substituent.        It is preferable that compounds having the above structure are        selected from Formula (S-1):

wherein:

-   -   R₁-R₁₅ are independently hydrogen, fluoro, cyano,        trifluoromethyl, sulfonyl, alkyl, aryl or substituted aryl        group.

Specific representative embodiments of the triarylboranes include:

The electron-transporting material can also be selected from substituted1,3,4-oxadiazoles of Formula (T):

wherein:

-   -   R₁ and R₂ are individually hydrogen; alkyl of from 1 to 24        carbon atoms, for example, propyl, t-butyl, heptyl, and the        like; aryl or hetero-atom substituted aryl of from 5 to 20        carbon atoms, for example, phenyl and naphthyl, furyl, thienyl,        pyridyl, quinolinyl and other heterocyclic systems; or halo such        as chloro, fluoro; or atoms necessary to complete a fused        aromatic ring.

Illustrative of the useful substituted oxadiazoles are the following:

The electron-transporting material can also be selected from substituted1,2,4-triazoles according to Formula (U):

wherein:

-   -   R₁, R₂, and R₃ are independently hydrogen, alkyl group, aryl or        substituted aryl group, and at least one of R₁-R₃ is aryl group        or substituted aryl group. An example of a useful triazole is        3-phenyl-4-(1-naphtyl)-5-phenyl-1,2,4-triazole represented by        formula (U-1):

The electron-transporting material can also be selected from substituted1,3,5-triazines. Examples of suitable materials are:

-   -   2,4,6-tris(diphenylamino)-1,3,5-triazine;    -   2,4,6-tricarbazolo-1,3,5-triazine;    -   2,4,6-tris(N-phenyl-2-naphthylamino)-1,3,5-triazine;    -   2,4,6-tris(N-phenyl-1-naphthylamino)-1,3,5-triazine;    -   4,4′,6,6′-tetraphenyl-2,2′-bi-1,3,5-triazine; and    -   2,4,6-tris([1,1′:3′,1″-terphenyl]-5′-yl)-1,3,5-triazine.

In addition, any of the metal chelated oxinoid compounds includingchelates of oxine itself (also commonly referred to as 8-quinolinol or8-hydroxyquinoline) of Formula (O) useful as host materials in a LEL arealso suitable for use in the ETL.

Some metal chelated oxinoid compounds having high triplet energy can beparticularly useful as an electron-transporting materials. Particularlyuseful aluminum or gallium complex host materials with high tripletenergy levels are represented by Formula (W).

In Formula (W), M₁ represents Al or Ga. R₂-R₇ represent hydrogen or anindependently selected substituent. Desirably, R₂ represents anelectron-donating group. Suitably, R₃ and R₄ each independentlyrepresent hydrogen or an electron donating substituent. A preferredelectron-donating group is alkyl such as methyl. Preferably, R₅, R₆, andR₇ each independently represent hydrogen or an electron-accepting group.Adjacent substituents, R₂-R₇, can combine to form a ring group. L is anaromatic moiety linked to the aluminum by oxygen, which can besubstituted with substituent groups such that L has from 6 to 30 carbonatoms.

Illustrative of useful chelated oxinoid compounds for use in the ETL isAluminum(III) bis(2-methyl-8-hydroxyquinoline)-4-phenylphenolate [alias,Balq].

The same anthracene derivatives according to Formula (P) useful as hostmaterials in the LEL can also be used in the ETL.

The thickness of the ETL is in the range of from 5 nm to 200 nm,preferably, in the range of from 10 nm to 150 nm.

Electron Injection Layer

In certain embodiments, the fluoranthene compound can be present in theelectron injection layer, as described previously. In some embodimentsof the invention, an alkali metal compound such as LiF or an organiclithium compound such as AM-2 is present in the EIL (138). Othersuitable materials can also be used in the EIL. For example, the EIL canbe an n-type doped layer containing at least one electron-transportingmaterial as a host and at least one n-type dopant. The dopant is capableof reducing the host by charge transfer. The term “n-type doped layer”means that this layer has semiconducting properties after doping, andthe electrical current through this layer is substantially carried bythe electrons.

The host in the EIL can be an electron-transporting material capable ofsupporting electron injection and electron transport. Theelectron-transporting material can be selected from theelectron-transporting materials for use in the ETL region as definedabove.

The n-type dopant in the n-type doped EIL can be is selected from alkalimetals, alkali metal compounds, alkaline earth metals, or alkaline earthmetal compounds, or combinations thereof. The term “metal compounds”includes organometallic complexes, metal-organic salts, and inorganicsalts, oxides and halides. Among the class of metal-containing n-typedopants, Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, La, Ce, Sm, Eu, Tb, Dy, orYb, and their compounds, are particularly useful. The materials used asthe n-type dopants in the n-type doped EIL also include organic reducingagents with strong electron-donating properties. By “strongelectron-donating properties” it is meant that the organic dopant shouldbe able to donate at least some electronic charge to the host to form acharge-transfer complex with the host. Nonlimiting examples of organicmolecules include bis(ethylenedithio)-tetrathiafulvalene(BEDT-TTF),tetrathiafulvalene(TTF), and their derivatives. In the case of polymerichosts, the dopant is any of the above or also a material molecularlydispersed or copolymerized with the host as a minor component.Preferably, the n-type dopant in the n-type doped EIL includes Li, Na,K, Rb, Cs, Mg, Ca, Sr, Ba, La, Ce, Nd, Sm, Eu, Tb, Dy, or Yb, orcombinations thereof. The n-type doped concentration is preferably inthe range of 0.01-20% by volume of this layer.

In a one embodiment, the electron-injection layer contains aphenanthroline derivative doped with a metal. Suitable metals includeLi, Na, K, Rb, Cs, Mg, Ca, Sr, Ba, La, Ce, Sm, Eu, Tb, Dy, or Yb withlithium being the most preferred. Suitable substituted phenanthrolinesfor this application include those according to formula (R), asdescribed previously.

The thickness of the EIL is often in the range of from 0.1 nm to 20 nm,and typically in the range of from 1 nm to 5 nm.

Cathode

When light emission is viewed solely through the anode, the cathode 140includes nearly any conductive material. Desirable materials haveeffective film-forming properties to ensure effective contact with theunderlying organic layer, promote electron injection at low voltage, andhave effective stability. Useful cathode materials often contain a lowwork function metal (<4.0 eV) or metal alloy. One preferred cathodematerial includes a Mg:Ag alloy as described in U.S. Pat. No. 4,885,221.Another suitable class of cathode materials includes bilayers includinga thin inorganic EIL in contact with an organic layer (e.g., organic EILor ETL), which is capped with a thicker layer of a conductive metal.Here, the inorganic EIL preferably includes a low work function metal ormetal salt and, if so, the thicker capping layer does not need to have alow work function. One such cathode includes a thin layer of LiFfollowed by a thicker layer of Al as described in U.S. Pat. No.5,677,572. Other useful cathode material sets include, but are notlimited to, those disclosed in U.S. Pat. Nos. 5,059,861; 5,059,862; and6,140,763.

When light emission is viewed through the cathode, cathode 140 should betransparent or nearly transparent. For such applications, metals shouldbe thin or one should use transparent conductive oxides, or includethese materials. Optically transparent cathodes have been described inmore detail in U.S. Pat. Nos. 4,885,211; 5,247,190; 5,703,436;5,608,287; 5,837,391; 5,677,572; 5,776,622; 5,776,623; 5,714,838;5,969,474; 5,739,545; 5,981,306; 6,137,223; 6,140,763; 6,172,459;6,278,236; 6,284,393; and EP Patent No. 1076368. Cathode materials aretypically deposited by thermal evaporation, electron beam evaporation,ion sputtering, or chemical vapor deposition. When needed, patterning isachieved through many well known methods including, but not limited to,through-mask deposition, integral shadow masking, for example asdescribed in U.S. Pat. No. 5,276,380 and EP Patent No. 0 732 868, laserablation, and selective chemical vapor deposition.

The thickness of the EIL is typically less than 20 nm, and preferably inthe range of 10 nm or less.

Substrate

OLED 100 is typically provided over a supporting substrate 110 whereeither the anode 120 or cathode 140 can be in contact with thesubstrate. The electrode in contact with the substrate is convenientlyreferred to as the bottom electrode. Conventionally, the bottomelectrode is the anode 120, but this invention is not limited to thatconfiguration. The substrate can either be light transmissive or opaque,depending on the intended direction of light emission. The lighttransmissive property is desirable for viewing the EL emission throughthe substrate. Transparent glass or plastic is commonly employed in suchcases. The substrate can be a complex structure comprising multiplelayers of materials. This is typically the case for active matrixsubstrates wherein TFTs are provided below the OLED layers. It is stillnecessary that the substrate, at least in the emissive pixelated areas,be comprised of largely transparent materials such as glass or polymers.For applications where the EL emission is viewed through the topelectrode, the transmissive characteristic of the bottom support isimmaterial, and therefore the substrate can be light transmissive, lightabsorbing or light reflective. Substrates for use in this case include,but are not limited to, glass, plastic, semiconductor materials such assilicon, ceramics, and circuit board materials. Again, the substrate canbe a complex structure comprising multiple layers of materials such asfound in active matrix TFT designs. It is necessary to provide in thesedevice configurations a light-transparent top electrode.

Deposition of Organic Layers

The organic materials mentioned above are suitably deposited throughsublimation, but can be deposited from a solvent with an optional binderto improve film formation. If the material is a polymer, solventdeposition is usually preferred. The material to be deposited bysublimation can be vaporized from a sublimator “boat” often comprised ofa tantalum material, e.g., as described in U.S. Pat. No. 6,237,529, orcan be first coated onto a donor sheet and then sublimed in closerproximity to the substrate. Layers with a mixture of materials canutilize separate sublimator boats or the materials can be pre-mixed andcoated from a single boat or donor sheet. Patterned deposition can beachieved using shadow masks, integral shadow masks (U.S. Pat. No.5,294,870), spatially-defined thermal dye transfer from a donor sheet(U.S. Pat. No. 5,851,709 and U.S. Pat. No. 6,066,357) and inkjet method(U.S. Pat. No. 6,066,357).

Organic materials useful in making OLEDs, for example organichole-transporting materials, organic light-emitting materials doped withan organic electroluminescent components have relatively complexmolecular structures with relatively weak molecular bonding forces, sothat care must be taken to avoid decomposition of the organicmaterial(s) during physical vapor deposition. The aforementioned organicmaterials are synthesized to a relatively high degree of purity, and areprovided in the form of powders, flakes, or granules. Such powders orflakes have been used heretofore for placement into a physical vapordeposition source wherein heat is applied for forming a vapor bysublimation or vaporization of the organic material, the vaporcondensing on a substrate to provide an organic layer thereon.

Several problems have been observed in using organic powders, flakes, orgranules in physical vapor deposition: These powders, flakes, orgranules are difficult to handle. These organic materials generally havea relatively low physical density and undesirably low thermalconductivity, particularly when placed in a physical vapor depositionsource which is disposed in a chamber evacuated to a reduced pressure aslow as 10⁻⁶ Torr. Consequently, powder particles, flakes, or granulesare heated only by radiative heating from a heated source, and byconductive heating of particles or flakes directly in contact withheated surfaces of the source. Powder particles, flakes, or granuleswhich are not in contact with heated surfaces of the source are noteffectively heated by conductive heating due to a relatively lowparticle-to-particle contact area; this can lead to nonuniform heatingof such organic materials in physical vapor deposition sources.Therefore, result in potentially nonuniform vapor-deposited organiclayers formed on a substrate.

These organic powders can be consolidated into a solid pellet. Thesesolid pellets consolidating into a solid pellet from a mixture of asublimable organic material powder are easier to handle. Consolidationof organic powder into a solid pellet can be accomplished withrelatively simple tools. A solid pellet formed from mixture comprisingone or more non-luminescent organic non-electroluminescent componentmaterials or luminescent electroluminescent component materials ormixture of non-electroluminescent component and electroluminescentcomponent materials can be placed into a physical vapor depositionsource for making organic layer. Such consolidated pellets can be usedin a physical vapor deposition apparatus.

In one aspect, the present invention provides a method of making anorganic layer from compacted pellets of organic materials on asubstrate, which will form part of an OLED.

One preferred method for depositing the materials of the presentinvention is described in US Publication No. 2004/0255857 and U.S. Pat.No. 7,288,286 where different source evaporators are used to evaporateeach of the materials of the present invention. A second preferredmethod involves the use of flash evaporation where materials are meteredalong a material feed path in which the material feed path istemperature controlled. Such a preferred method is described in thefollowing co-assigned patent applications: U.S. Pat. Nos. 7,232,588;7,238,389; 7,288,285; 7,288,286; 7,165,340; and US Publication No.2006/0177576. Using this second method, each material can be evaporatedusing different source evaporators or the solid materials can be mixedprior to evaporation using the same source evaporator.

Encapsulation

Most OLED devices are sensitive to moisture or oxygen so they arecommonly sealed in an inert atmosphere such as nitrogen or argon, alongwith a desiccant such as alumina, bauxite, calcium sulfate, clays,silica gel, zeolites, alkaline metal oxides, alkaline earth metaloxides, sulfates, or metal halides and perchlorates. Methods forencapsulation and desiccation include, but are not limited to, thosedescribed in U.S. Pat. No. 6,226,890.

OLED Device Design Criteria

For full color display, the pixelation of LELs can be needed. Thispixelated deposition of LELs is achieved using shadow masks, integralshadow masks, U.S. Pat. No. 5,294,870, spatially defined thermal dyetransfer from a donor sheet, U.S. Pat. Nos. 5,688,551; 5,851,709; and6,066,357; and inkjet method, U.S. Pat. No. 6,066,357.

OLEDs of this invention can employ various well-known optical effects inorder to enhance their emissive properties if desired. This includesoptimizing layer thicknesses to yield improved light transmission,providing dielectric mirror structures, replacing reflective electrodeswith light-absorbing electrodes, providing anti-glare or anti-reflectioncoatings over the display, providing a polarizing medium over thedisplay, or providing colored, neutral density, or color-conversionfilters over the display. Filters, polarizers, and anti-glare oranti-reflection coatings can be specifically provided over the OLED oras part of the OLED.

Embodiments of the invention can provide EL devices that have goodluminance efficiency, good operational stability, and reduced drivevoltages. Embodiments of the invention can also give reduced voltagerises over the lifetime of the devices and can be produced with highreproducibility and consistently to provide good light efficiency. Theycan have lower power consumption requirements and, when used with abattery, provide longer battery lifetimes.

The invention and its advantages are further illustrated by the specificexamples that follow. The term “percentage” or “percent” and the symbol“%” indicate the volume percent (or a thickness ratio as measured on athin film thickness monitor) of a particular first or second compound ofthe total material in the layer of the invention and other components ofthe devices. If more than one second compound is present, the totalvolume of the second compounds can also be expressed as a percentage ofthe total material in the layer of the invention.

EXAMPLE 1 Synthesis of Inventive Compound Inv-1

Inv-1 was synthesized as outlined in Scheme 1 and described below.

Preparation of 7,9-Diphenyl-8H-Cyclopent[a]acenaphthylen-8-one (1)

7,9-Diphenyl-8H-Cyclopent[a]acenaphthylen-8-one, (Acecyclone), (1) wasprepared according to the procedure of W. Dilthey, I. ter Horst and W.Schommer; Journal fuer Praktische Chemie (Leipzig), 143, (1935),189-210.

Preparation of 8-pyrid-3′-yl-7,10-diphenylfluoranthene (Inv-1)

Acecyclone (5.6 g, 16.0 mMol) and 2-ethynylpyridine (2.16 g, 21 mMol)were heated in 1,2-dichlorobenzene (50 mL) at 200° C. for 3 hours. Afterthis period, the solution was cooled and added directly to a column ofsilica gel. Using pressure chromatography and eluting initially withheptane, 1,2-dichlorobenzene was removed. A gradient of ethylacetate/heptane up to 50% ethyl acetate was then used to obtain asolution of product. After removal of most of the solvent (heptane/ethylacetate) by evaporation, the product began to crystallize from thesolution. The solution was treated with methanol and the yellow solidobtained was rinsed from the flask and washed with methanol and thendried. This afforded 4.3 g of Inv-1, mp 195° C. Before use in devicefabrication, Inv-1 was sublimed at 190° C./3×10⁻¹ Torr.

EXAMPLE 2 Electrochemical Redox Potentials and Estimated Energy Levels

LUMO and HOMO values are typically estimated experimentally byelectrochemical methods. The following method illustrates a useful wayto measure redox properties. A Model CHI660 electrochemical analyzer (CHInstruments, Inc., Austin, Tex.) was employed to carry out theelectrochemical measurements. Cyclic voltammetry (CV) and Osteryoungsquare-wave voltammetry (SWV) were used to characterize the redoxproperties of the compounds of interest. A glassy carbon (GC) diskelectrode (A=0.071 cm²) was used as working electrode. The GC electrodewas polished with 0.05 μm alumina slurry, followed by sonicationcleaning in Milli-Q deionized water twice and rinsed with acetone inbetween water cleaning. The electrode was finally cleaned and activatedby electrochemical treatment prior to use. A platinum wire served ascounter electrode and a saturated calomel electrode (SCE) was used as aquasi-reference electrode to complete a standard 3-electrodeelectrochemical cell. Ferrocene (Fc) was used as an internal standard(E_(Fc)=0.50 V vs. SCE in 1:1 acetonitrile/toluene, 0.1 M TBAF). Amixture of acetonitrile and toluene (50%/50% v/v, or 1:1) was used asthe organic solvent system. The supporting electrolyte,tetrabutylammonium tetrafluoroborate (TBAF) was recrystallized twice inisopropanol and dried under vacuum. All solvents used were low watergrade (<20 ppm water). The testing solution was purged with high puritynitrogen gas for approximately 5 minutes to remove oxygen and a nitrogenblanket was kept on the top of the solution during the course of theexperiments. All measurements were performed at ambient temperature of25±1° C. The oxidation and reduction potentials were determined eitherby averaging the anodic peak potential (Ep,a) and cathodic peakpotential (Ep,c) for reversible or quasi-reversible electrode processesor on the basis of peak potentials (in SWV) for irreversible processes.LUMO and HOMO values are calculated from the following equations:

Formal reduction potentials vs. SCE for reversible or quasi-reversibleprocesses;E ^(O)′_(red)=(E _(pa) +E _(pc))/2E ^(O)′_(ox)=(E _(pa) +E _(pc))/2Formal reduction potentials vs. Fc;E ^(O)′_(red)vs.Fc=(E ^(O)′_(red)vs. SCE)−E _(Fc)E ^(O)′_(ox)vs.Fc=(E ^(O)′_(ox)vs. SCE)−E _(Fc)

-   where E_(Fc) is the oxidation potential E_(ox), of ferrocene;    Estimated lower limit for LUMO and HOMO vlaues;    LUMO=HOMO_(Fc)−(E ^(O)′_(red)vs.Fc)    HOMO=HOMO_(Fc)−(E ^(O)′_(ox)vs.Fc)

where HOMO_(Fc) (Highest Occupied Molecular Orbital for ferrocene)=−4.8eV.

Redox potentials as well as estimated HOMO and LUMO values aresummarized in Table 1.

TABLE 1 Redox Potentials and Estimated Energy Levels. E^(o/)(ox)E^(o/)(red) E^(o/)(ox) V vs. V vs. V vs. E^(o/)(red) HOMO LUMO CompoundSCE SCE FC V vs. FC (eV) (eV) Inv-1 1.60 −1.667 1.17 −2.17 −5.97 −2.63Inv-3 — −1.628 — −2.13 — −2.67 Inv-6 1.67 −1.647 1.17 −2.15 −5.97 −2.65FA-1 1.67 −1.67 1.17 −2.19 −5.97 −2.61 FA-2/FA-3* 1.67 −1.64 1.17 −2.14−5.97 −2.66 P-2 1.308 −1.855 0.808 −2.355 −5.61 −2.44 P-4 1.345 −1.8470.845 −2.347 −5.64 −2.45 *A 60/40 mixture of isomers FA-2 and FA-3

One can see from Table 1 that the estimated LUMO energy values offluoranthene derivatives FA-1 and FA-2/FA-3 mixture are very close(within 0.1 eV) of those of Inv-1, Inv-3, and Inv-6. The anthracenes P-2and P-3 have estimated LUMO values within about 0.2 eV of the inventivecompounds.

EXAMPLE 3 Preparation of Blue-Light Emitting OLED Devices 3.1 through3.6

A series of OLED devices (3.1 through 3.6) were constructed in thefollowing manner:

-   -   1. A glass substrate coated with an 85 nm layer of indium-tin        oxide (ITO), as the anode, was sequentially ultrasonicated in a        commercial detergent, rinsed in deionized water and exposed to        oxygen plasma for about 1 min.    -   2. Over the ITO was deposited a 1 nm fluorocarbon (CF_(x))        hole-injecting layer (HIL) by plasma-assisted deposition of CHF₃        as described in U.S. Pat. No. 6,208,075.    -   3. Next a layer of hole-transporting material        4,4′-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) was        deposited to a thickness of 95 nm.    -   4. A 20 nm light-emitting layer (LEL) corresponding to the host        material P-4 and 1.5% by volume of FD-54 was then deposited.    -   5. An electron-transporting layer (ETL) consisting of a mixture        of isomeric compounds FA-2 and FA-3 (60/40 ratio) at a thickness        as shown in Table 2, was vacuum-deposited over the LEL.    -   6. For devices 3.2 through 3.6, an electron-injecting layer        (EIL) corresponding to Inv-1 was vacuum deposited onto the ETL        at a thickness as shown in Table 2.    -   7. And finally, a 100 nm layer of aluminum was deposited onto        the EIL, to form the cathode. For device 3.1, this layer was        deposited on the ETL.

The above sequence completes the deposition of the EL device. The devicewas then hermetically packaged in a dry glove box for protection againstambient environment.

During their preparation each device was duplicated to give fouridentically fabricated devices for each example (except for examples 3.1and 3.2). The devices thus formed were tested for drive voltage andluminous efficiency at an operating current of 20 mA/cm². For 3.3through 3.6 the results for the four duplicate devices were average andthe results are reported in Table 2.

TABLE 2 Performance of Devices 3.1-3.6. ETL EIL Drive Example(FA-2/FA-3) Level Volt. Efficiency (Type) Level (nm) EIL (nm) (Volts)(cd/A) 3.1 35.0 — 0.0 13.5 0.025 (Comparative) 3.2 34.0 Inv-1 1.0 13.50.17 (Inventive) 3.3 33.0 Inv-1 2.0 10.2 2.3 (Inventive) 3.4 30.0 Inv-15.0 8.6 3.3 (Inventive) 3.5 27.5 Inv-1 7.5 8.5 3.2 (Inventive) 3.6 25.0Inv-1 10.0 8.3 3.2 (Inventive)

All the devices have the same thickness; however, comparative device 3.1does not contain Inv-1 as an electron-injecting material. One can seefrom Table 2 that by adding a layer of Inv-1 between theelectron-transporting layer and the cathode (devices 3.2 through 3.6)one obtains significantly higher luminance relative to the comparative.As the level of Inv-1 increases from device 3.2 to 3.6, the drivevoltage decreases.

EXAMPLE 4 Preparation of Blue-Light Emitting OLED Devices 4.1 through4.12

A series of OLED devices (4.1 through 4.6) were constructed in thefollowing manner:

-   -   1. A glass substrate coated with an 85 nm layer of indium-tin        oxide (ITO), as the anode, was sequentially ultrasonicated in a        commercial detergent, rinsed in deionized water and exposed to        oxygen plasma for about 1 min.    -   2. Over the ITO was deposited a 1 nm fluorocarbon (CF_(x))        hole-injecting layer (HIL) by plasma-assisted deposition of CHF₃        as described in U.S. Pat. No. 6,208,075.    -   3. Next a layer of hole-transporting material        4,4′-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) was        deposited to a thickness of 95 nm.    -   4. A 20 nm light-emitting layer (LEL) corresponding to the host        material P-4 and 1.5% by volume of FD-54 was then deposited.    -   5. An electron-transporting layer (ETL) consisting of FA-2 and        FA-3 (60/40 ratio) at a thickness as shown in Table 3, was        vacuum-deposited over the LEL.    -   6. For devices 4.2 through 4.6, a first electron-injecting layer        (EIL1) corresponding to Inv-1 was vacuum deposited onto the ETL        at a thickness as shown in Table 3.    -   7. A second electron-injecting layer (EIL2) corresponding to LiF        at a thickness of was 0.5 nm was vacuum deposited onto EIL1. For        device 4.1 this layer was deposited directly on the ETL.    -   8. And finally, a 100 nm layer of aluminum was deposited onto        the EIL2, to form the cathode.

The above sequence completes the deposition of the EL device. The devicewas then hermetically packaged in a dry glove box for protection againstambient environment.

Devices 4.7 through 4.12 were prepared in the same manner as Devices 4.1through 4.6, except Inv-1, when present, was replaced with C-1 in thefirst electron-injecting layer (ET1), see Table 3.

During their preparation each device was duplicated to give fouridentically fabricated devices for each example. The devices thus formedwere tested for drive voltage and luminous efficiency at an operatingcurrent of 20 mA/cm². The results from the four duplicate devices wereaveraged and the results are reported in Table 3.

TABLE 3 Performance of Devices 4.1-4.12 ETL Drive Example (FA-2/FA-3)EIL1 EIL2 (LiF) Volt. Efficiency (Type) Level (nm) EIL1 Level (nm) Level(nm) (Volts) (cd/A) 4.1 35.0 — — 0.5 10.8 2.2 (Comparative) 4.2 34.0Inv-1 1.0 0.5 5.1 6.4 (Inventive) 4.3 33.0 Inv-1 2.0 0.5 4.9 6.3(Inventive) 4.4 30.0 Inv-1 5.0 0.5 5.0 6.3 (Inventive) 4.5 27.5 Inv-17.5 0.5 5.2 6.2 (Inventive) 4.6 25.0 Inv-1 10.0  0.5 5.3 6.1 (Inventive)4.7 35.0 — — 0.5 9.1 2.3 (Comparative) 4.8 34.0 C-1 1.0 0.5 6.3 5.0(Comparative) 4.9 33.0 C-1 2.0 0.5 5.9 5.5 (Comparative) 4.10 30.0 C-15.0 0.5 8.2 2.8 (Comparative) 4.11 27.5 C-1 7.5 0.5 8.3 2.7(Comparative) 4.12 25.0 C-1 10.0  0.5 7.6 2.9 (Comparative)

From Table 3, inventive devices 4.2 through 4.6, it can be seen thatdevices having a first electron-injecting layer consisting of Inv-1 anda second electron-injecting layer formed from LiF provide extremely lowdrive voltage and high luminance, especially compared to device 4.1,which does not contain Inv-1.

Comparative devices 4.7 through 4.12 were constructed in the same manneras inventive devices 4.1 through 4.6, except Inv-1, when present, wasreplaced with an electron-injecting material that contains more than onefluoranthene nucleus, C-1. One can see from Table 3 that the eachinventive device containing Inv-1 provides lower drive voltage andhigher luminance efficiency relative to its corresponding comparativedevice containing C-1 (e.g., device 4.4 versus 4.10). Compound C-1 issimilar in structure to materials described in US Publication No.2006/0097227, which contain more than one fluoranthene nucleus.

EXAMPLE 5 Preparation of Blue-Light Emitting OLED Devices 5.1 through5.6

A series of OLED devices (5.1 through 5.6) were constructed in the samemanner as devices 4.1 through 4.6, except Inv-1, when present, wasreplaced with Inv-2. During their preparation each device was duplicatedto give four identically fabricated devices for each example. Thedevices thus formed were tested for drive voltage and luminousefficiency at an operating current of 20 mA/cm². The results from thefour duplicate devices were averaged and the results are reported inTable 4.

TABLE 4 Performance of Devices 5.1-5.6. ETL Drive Example (FA-2/FA-3)EIL1 EIL2 (LiF) Volt. Efficiency (Type) Level (nm) EIL1 Level (nm) Level(nm) (Volts) (cd/A) 5.1 35.0 — 0.0 0.5 9.3 2.1 (Comparative) 5.2 34.0Inv-2 1.0 0.5 8.0 2.7 (Inventive) 5.3 33.0 Inv-2 2.0 0.5 7.2 3.1(Inventive) 5.4 30.0 Inv-2 5.0 0.5 5.9 4.1 (Inventive) 5.5 27.5 Inv-27.5 0.5 5.3 4.7 (Inventive) 5.6 25.0 Inv-2 10.0 0.5 5.5 4.1 (Inventive)

From Table 4 it can be seen that devices 5.2 to 5.6, having a firstelectron-injecting layer (EIL1) corresponding to Inv-2, provide lowerdrive voltage and higher efficiency relative to device 5.1, which doesnot contain Inv-2 even though all he devices have the same thickness.

EXAMPLE 6 Preparation of Red-Light Emitting Devices 6.1 through 6.12

A series of OLED devices (6.1 through 6.6) were constructed in thefollowing manner:

-   -   1. A glass substrate coated with an 85 nm layer of indium-tin        oxide (ITO), as the anode, was sequentially ultrasonicated in a        commercial detergent, rinsed in deionized water and exposed to        oxygen plasma for about 1 min.    -   2. Over the ITO was deposited a 1 nm fluorocarbon (CF_(x))        hole-injecting layer (HIL) by plasma-assisted deposition of CHF₃        as described in U.S. Pat. No. 6,208,075.    -   3. Next a layer of hole-transporting material        4,4′-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) was        deposited to a thickness of 144.0 nm.    -   4. A 40 nm light-emitting layer (LEL) corresponding to a first        host material rubrene (FD-5, see Table 5 for level), and a        second host material FA-1 (see Table 5 for level) and 0.5% by        volume of dopant FD-46 was then deposited.    -   5. An electron-transporting layer (ETL) of FA-1 at a thickness        of 30 nm was vacuum-deposited over the LEL.    -   6. A first electron-injecting layer (EIL1) corresponding to        Inv-1 was vacuum deposited onto the ETL at a thickness of 5 nm.    -   7. A second electron-injecting layer (EIL2) corresponding to LiF        at a thickness of was 0.5 nm was vacuum deposited onto EIL1.    -   8. And finally, a 100 nm layer of aluminum was deposited onto        the EIL2, to form the cathode.

The above sequence completes the deposition of the EL device. The devicewas then hermetically packaged in a dry glove box for protection againstambient environment.

Devices 5.6 through 5.12 were prepared in the same manner as Devices 5.1through 5.6 except compound FA-1 was replaced with compounds FA-2 andFA-3 (60/40 ratio) in the EML and ETL (Table 5).

During their preparation each device was duplicated to give fouridentically fabricated devices for each example. The devices thus formedwere tested for drive voltage and luminous efficiency at an operatingcurrent of 20 mA/cm². The results from the four duplicate devices wereaveraged and the results are reported in Table 5.

TABLE 5 Performance of Devices 6.1-6.12. EML Host EML Example (Rubrene)EML Co-Host ETL EIL-1 Drive Volt. Efficiency (Type) % Level Co-Host %Level (30 nm) 5.0 nm (Volts) (cd/A) 6.1 79.5 FA-1 20.0 FA-1 Inv-1 4.810.5 (Inventive) 6.2 74.5 FA-1 25.0 FA-1 Inv-1 4.8 11.2 (Inventive) 6.369.5 FA-1 30.0 FA-1 Inv-1 4.9 10.6 (Inventive) 6.4 64.5 FA-1 35.0 FA-1Inv-1 4.9 10.5 (Inventive) 6.5 59.5 FA-1 40.0 FA-1 Inv-1 4.8 10.8(Inventive) 6.6 54.5 FA-1 45.0 FA-1 Inv-1 4.8 10.4 (Inventive) 6.7 79.5FA-2/ 20.0% FA-2/ Inv-1 4.8 11.5 (Inventive) FA-3 FA-3 6.8 74.5 FA-2/25.0 FA-2/ Inv-1 4.8 13.1 (Inventive) FA-3 FA-3 6.9 69.5 FA-2/ 30.0FA-2/ Inv-1 4.9 13.1 (Inventive) FA-3 FA-3 6.10 64.5 FA-2/ 35.0 FA-2/Inv-1 4.9 13.2 (Inventive) FA-3 FA-3 6.11 59.5 FA-2/ 40.0 FA-2/ Inv-14.9 12.6 (Inventive) FA-3 FA-3 6.12 54.5 FA-2/ 45.0 FA-2/ Inv-1 5.0 11.5(Inventive) FA-3 FA-3

Inventive devices 6.1 through 6.12 demonstrate that very efficientred-light emitting devices can be prepared using Inv-1 in a firstelectron-injecting layer and LiF in a second electron-injecting layer.In this case, one obtains the best performance when the emitting layerand the electron-transporting layer both contain the isomeric mixture offluoranthene derivatives FA-2 and FA-3 (devices 6.7 through 6.12)relative to the case when the layers contain fluoranthene derivativeFA-1 (devices 6.1 through 6.6). The devices also provide low drivevoltage.

EXAMPLE 7 Preparation of Blue-light Emitting Devices 7.1 through 7.6

A series of OLED devices (7.1 through 7.6) were constructed in thefollowing manner:

-   -   1. A glass substrate coated with an 85 nm layer of indium-tin        oxide (ITO), as the anode, was sequentially ultrasonicated in a        commercial detergent, rinsed in deionized water and exposed to        oxygen plasma for about 1 min.    -   2. Over the ITO was deposited a 1 nm fluorocarbon (CF_(x))        hole-injecting layer (HIL) by plasma-assisted deposition of CHF₃        as described in U.S. Pat. No. 6,208,075.    -   3. Next a layer of hole-transporting material        4,4′-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) was        deposited to a thickness of 95.0 nm.    -   4. A 20 nm light-emitting layer (LEL) corresponding to a first        host material P-4 (see Table 6 for level) and a second host        material Inv-1 (see Table 6 for level) and 1.5% by volume of        dopant FD-54 was then deposited.    -   5. An electron-transporting layer (ETL) corresponding to Inv-1        at a thickness of 35 nm was vacuum-deposited over the LEL.    -   6. An electron-injecting layer (EIL) corresponding to AM-1 was        vacuum deposited onto the ETL at a thickness of 3.5 nm.    -   7. And finally, a 100 nm layer of aluminum was deposited onto        the EIL, to form the cathode.

The above sequence completes the deposition of the EL device. The devicewas then hermetically packaged in a dry glove box for protection againstambient environment.

During their preparation each device was duplicated to give fouridentically fabricated devices for each example. The devices thus formedwere tested for drive voltage and luminous efficiency at an operatingcurrent of 20 mA/cm². The results from the four duplicate devices wereaveraged and the results are reported in Table 6.

TABLE 6 Results for devices 7.1 through 7.6. EML EML Co-Host Host DriveEffi- Example (Inv-1) (P-4) ETL EIL Volt. ciency (Type) % Level % Level(35 nm) (3.5 nm) (Volts) (cd/A) 7.1 0.0 98.5 Inv-1 AM-1 7.9 6.5(Inventive) 7.2 5.0 93.5 Inv-1 AM-1 7.5 5.9 (Inventive) 7.3 10.0 88.5Inv-1 AM-1 7.5 5.9 (Inventive) 7.4 30.0 68.5 Inv-1 AM-1 6.5 4.9(Inventive) 7.5 50.0 48.5 Inv-1 AM-1 6.5 3.8 (Inventive) 7.6 98.5 0.0Inv-1 AM-1 7.4 2.3 (Inventive)

This example illustrates the use of Inv-1 as both anelectron-transporting material and as a co-host in the light-emittinglayer. It also shows the use of Inv-1 in the ETL in combination with theorganic lithium compound AM-1 in the EIL. One can see from Table 6 that,on average, devices provide very good performance characteristics.

EXAMPLE 8 Preparation of Blue-light Emitting Devices 8.1 through 8.6

A series of OLED devices (8.1 through 8.6) were constructed in thefollowing manner:

-   -   1. A glass substrate coated with an 85 nm layer of indium-tin        oxide (ITO), as the anode, was sequentially ultrasonicated in a        commercial detergent, rinsed in deionized water and exposed to        oxygen plasma for about 1 min.    -   2. Over the ITO was deposited a 1 nm fluorocarbon (CF_(x))        hole-injecting layer (HIL) by plasma-assisted deposition of CHF₃        as described in U.S. Pat. No. 6,208,075.    -   3. Next a layer of hole-transporting material        4,4′-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) was        deposited to a thickness of 95.0 nm.    -   4. A 20 nm light-emitting layer (LEL) corresponding to a first        host material P-4 (see Table 7 for level) and a second host        material FA-4 (see Table 7 for level) and 1.5% by volume of        dopant FD-54 was then deposited.    -   5. An electron-transporting layer (ETL) corresponding to FA-4 at        a thickness of 30.0 nm was vacuum-deposited over the LEL.    -   6. A first electron-injecting layer (EIL1) corresponding to        Inv-1 was vacuum deposited onto the ETL at a thickness of 5 nm.    -   7. A second electron-injecting layer (EIL2) corresponding to LiF        at a thickness of was 0.5 nm was vacuum deposited onto the ETL1        layer.    -   8. And finally, a 100 nm layer of aluminum was deposited onto        the EIL2, to form the cathode.

The above sequence completes the deposition of the EL device. The devicewas then hermetically packaged in a dry glove box for protection againstambient environment.

During their preparation each device was duplicated to give fouridentically fabricated devices for each example. The devices thus formedwere tested for drive voltage and luminous efficiency at an operatingcurrent of 20 mA/cm². The results from the four duplicate devices wereaveraged and the results are reported in Table 7.

TABLE 7 Results for devices 8.1 through 8.6. EML EML Host Co-Host DriveEffi- Example (P-4) (FA-4) ETL EIL1 Volt. ciency (Type) % Level % Level(35 nm) (3.5 nm) (Volts) (cd/A) 8.1 98.5 0.0 FA-4 Inv-1 5.1 6.1(Inventive) 8.2 93.5 5.0 FA-4 Inv-1 5.2 6.1 (Inventive) 8.3 88.5 10.0FA-4 Inv-1 5.1 5.8 (Inventive) 8.4 68.5 30.0 FA-4 Inv-1 5.1 5.0(Inventive) 8.5 48.5 50.0 FA-4 Inv-1 5.0 2.9 (Inventive) 8.6 0.0 98.5FA-4 Inv-1 4.9 4.1 (Inventive)

This example illustrates the use of an EIL1 containing Inv-1, an EIL2having LiF, and an ETL using a fluoranthene derivative, FA-4. The LELcontains an anthracene derivative (P-4) or a fluoranthene derivativeFA-4, or a mix thereof. One can see from Table 7 that, on average,devices are obtained with low drive voltage and high efficiency.

EXAMPLE 9 Preparation of Blue-light Emitting Devices 9.1 through 9.6

A series of OLED devices (9.1 through 9.6) were constructed in thefollowing manner:

-   -   1. A glass substrate coated with an 85 nm layer of indium-tin        oxide (ITO), as the anode, was sequentially ultrasonicated in a        commercial detergent, rinsed in deionized water and exposed to        oxygen plasma for about 1 min.    -   2. Over the ITO was deposited a 1 nm fluorocarbon (CF_(x))        hole-injecting layer (HIL) by plasma-assisted deposition of CHF₃        as described in U.S. Pat. No. 6,208,075.    -   3. Next a layer of hole-transporting material        4,4′-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) was        deposited to a thickness of 95.0 nm.    -   4. A 20 nm light-emitting layer (LEL) corresponding to a host        material P-4 and 1.5% by volume of dopant FD-54 was then        deposited.    -   5. A 35.0 nm electron-transporting layer (ETL) corresponding to        a mixture of Inv-1 and AM-2 (see Table 8 for amounts) was vacuum        over the LEL.    -   6. And finally, a 100 nm layer of aluminum was deposited onto        the EIL, to form the cathode.

The above sequence completes the deposition of the EL device. The devicewas then hermetically packaged in a dry glove box for protection againstambient environment.

During their preparation each device was duplicated to give fouridentically fabricated devices for each example. The devices thus formedwere tested for drive voltage and luminous efficiency at an operatingcurrent of 20 mA/cm². The results from the four duplicate devices wereaveraged and the results are reported in Table 8.

TABLE 8 Results for devices 9.1 through 9.6. ETL ETL Host Co-Host DriveExample (Inv-1) (AM-2) Volt. Efficiency (Type) % Level % Level (Volts)(cd/A) 9.1 100 0 7.0 2.9 (Inventive) 9.2 80 20 5.3 4.8 (Inventive) 9.360 40 5.4 4.9 (Inventive) 9.4 50 50 5.5 4.8 (Inventive) 9.5 40 60 6.04.4 (Inventive) 9.6 25 75 7.9 2.9 (Inventive)

This example illustrates the use of a mixture of Inv-1 and the organiclithium compound, AM-2, in an electron-transporting layer and whereinthe devices do not have an electron-injecting layer. On can see fromTable 8 that the mixture provides a synergistic effect affording devices(9.2-9.5) with especially low voltage and good efficiency relative tothe case where Inv-1 is used alone (9.1) or where the ETL is mainlycomposed of AM-2 (9.6).

EXAMPLE 10 Preparation of Red-light Emitting Devices 10.1 through 10.6

A series of OLED devices (10.1 through 10.6) were constructed in thefollowing manner:

-   -   1. A glass substrate coated with an 85 nm layer of indium-tin        oxide (ITO), as the anode, was sequentially ultrasonicated in a        commercial detergent, rinsed in deionized water and exposed to        oxygen plasma for about 1 min.    -   2. Over the ITO was deposited a 1 nm fluorocarbon (CF_(x))        hole-injecting layer (HIL) by plasma-assisted deposition of CHF₃        as described in U.S. Pat. No. 6,208,075.    -   3. Next a layer of hole-transporting material        4,4′-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) was        deposited to a thickness of 144.0 nm.    -   4. A 40.0 nm light-emitting layer (LEL) corresponding to a first        host material, rubrene, (FD-5 see Table 9 for level) and a        second host material, Inv-1 (see Table 9 for level) and 0.5% by        volume of dopant FD-46 was then deposited.    -   5. An electron-transporting layer (ETL) of Inv-1 at a thickness        of 35.0 nm was vacuum-deposited over the LEL.    -   6. An electron-injecting layer (EIL) corresponding to LiF at a        thickness of 0.5 nm was vacuum deposited onto the ETL1 layer    -   7. And finally, a 100 nm layer of aluminum was deposited onto        the EIL, to form the cathode.

The above sequence completes the deposition of the EL device. The devicewas then hermetically packaged in a dry glove box for protection againstambient environment.

During their preparation each device was duplicated to give fouridentically fabricated devices for each example. The devices thus formedwere tested for drive voltage and luminous efficiency at an operatingcurrent of 20 mA/cm². The results from the four duplicate devices wereaveraged and the results are reported in Table 9.

TABLE 9 Results for devices 10.1 through 10.6. EML EML Host Co-HostDrive Example (Rubrene) (Inv-1) ETL Volt. Efficiency (Type) % Level %Level 35.0 nm (Volts) (cd/A) 10.1 99.5 0.0 Inv-1 5.2 7.9 (Inventive)10.2 89.75 10.0 Inv-1 5.5 8.8 (Inventive) 10.3 79.75 20.0 Inv-1 5.2 9.7(Inventive) 10.4 49.75 50.0 Inv-1 5.4 9.7 (Inventive) 10.5 29.75 70.0Inv-1 5.5 7.5 (Inventive) 10.6 0.00 99.5 Inv-1 7.3 1.3 (Inventive)

Example 10 illustrates the use of Inv-1 in the LEL as a co-host withrubrene (10.2-10.5) or as a host material (10.6). In each case Inv-1 isalso used in the ETL. From Table 9, it can be seen that, on average, oneobtains devices with good performance characteristics. This isespecially true for devices 10.3 and 10.4 wherein Inv-1 is a co-host inthe LEL.

EXAMPLE 11 Preparation of Blue-light Emitting Devices 11.1 through 11.6

A series of OLED devices (11.1 through 11.6) were constructed in thefollowing manner:

-   -   1. A glass substrate coated with an 85 nm layer of indium-tin        oxide (ITO), as the anode, was sequentially ultrasonicated in a        commercial detergent, rinsed in deionized water and exposed to        oxygen plasma for about 1 min.    -   2. Over the ITO was deposited a 1 nm fluorocarbon (CF_(x))        hole-injecting layer (HIL) by plasma-assisted deposition of CHF₃        as described in U.S. Pat. No. 6,208,075.    -   3. Next a layer of hole-transporting material        4,4′-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) was        deposited to a thickness of 95.0 nm.    -   4. A 20 nm light-emitting layer (LEL) corresponding to a host        material P-2 and 3.0% by volume of dopant FD-47 was then        deposited.    -   5. A 35.0 nm electron-transporting layer (ETL) corresponding to        a mixture of isomers FA-2 and FA-3 (60/40 ratio) and Inv-1 (see        Table 10 for levels) was vacuum over the LEL.    -   6. An electron-injecting layer (EIL) corresponding to LiF at a        thickness of was 0.5 nm was vacuum deposited onto the ETL layer.    -   7. And finally, a 100 nm layer of aluminum was deposited onto        the EIL, to form the cathode.

The above sequence completes the deposition of the EL device. The devicewas then hermetically packaged in a dry glove box for protection againstambient environment.

During their preparation each device was duplicated to give fouridentically fabricated devices for each example. The devices thus formedwere tested for drive voltage and luminous efficiency at an operatingcurrent of 20 mA/cm². The results from the four duplicate devices wereaveraged and the results are reported in Table 10.

TABLE 10 Results for devices 11.1 through 11.6. ETL Host ETL (FA-2/Co-Host Drive Example FA-3) (Inv-1) Volt. Efficiency (Type) % Level %Level (Volts) (cd/A) 11.1 90 10 7.4 12.1 (Inventive) 11.2 80 20 5.8 14.8(Inventive) 11.3 70 30 5.0 15.5 (Inventive) 11.4 50 50 4.6 16.3(Inventive) 11.5 25 75 4.6 15.9 (Inventive) 11.6 0 100 4.6 13.6(Inventive)

Example 11 demonstrates the use of Inv-1 in the ETL in combination withelectron-transporting fluoranthene derivatives FA-2and FA-3. As can beseen from Table 10, the combination can afford very high efficiency atlow drive voltage (e.g., device 11.4).

EXAMPLE 12 Preparation of Blue-light Emitting Devices 12.1 through 12.6

A series of OLED devices (12.1 through 12.6) were constructed in thefollowing manner:

-   -   1. A glass substrate coated with an 85 nm layer of indium-tin        oxide (ITO), as the anode, was sequentially ultrasonicated in a        commercial detergent, rinsed in deionized water and exposed to        oxygen plasma for about 1 min.    -   2. Over the ITO was deposited a 1 nm fluorocarbon (CF_(x))        hole-injecting layer (HIL) by plasma-assisted deposition of CHF₃        as described in U.S. Pat. No. 6,208,075.    -   3. Next a layer of hole-transporting material        4,4′-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) was        deposited to a thickness of 95.0 nm.    -   4. A 20 nm light-emitting layer (LEL) corresponding to a host        material P-4 and 1.5% by volume of dopant FD-54 was then        deposited.    -   5. An electron-transporting layer (ETL) corresponding to an        isomeric mixture of FA-2 and FA-3 (60/40 ratio, see Table 11 for        levels) was vacuum-deposited over the LEL.    -   6. For devices 12.2 through 12.6, a first electron-injecting        layer (EIL1) corresponding to Inv-3 (see Table 11 for levels)        was vacuum deposited onto the ETL.    -   7. A second electron-injecting layer (EIL2) corresponding to LiF        at a thickness of was 0.5 nm was vacuum deposited onto the EIL1.        For device 12.1, this layer was deposited directly on the ETL.    -   8. And finally, a 100 nm layer of aluminum was deposited onto        the EIL, to form the cathode.

The above sequence completes the deposition of the EL device. The devicewas then hermetically packaged in a dry glove box for protection againstambient environment.

During their preparation each device was duplicated to give fouridentically fabricated devices for each example. The devices thus formedwere tested for drive voltage and luminous efficiency at an operatingcurrent of 20 mA/cm². The results from the four duplicate devices wereaveraged and the results are reported in Table 11.

TABLE 11 Results for devices 12.1 through 12.18. ETL Drive Example(FA-2/FA-3) EIL1 Volt. Efficiency (Type) Level (nm) EIL1 Level (nm)(Volts) (cd/A) 12.1 35.0 — — 12.3 0.55 (Comparative) 12.2 34.0 Inv-3 1.08.6 3.2 (Inventive) 12.3 32.5 Inv-3 2.5 7.5 4.2 (Inventive) 12.4 30.0Inv-3 5.0 7.5 4.0 (Inventive) 12.5 25.0 Inv-3 10.0 7.6 3.8 (Inventive)12.6 15.0 Inv-3 20.0 7.2 3.7 (Inventive)

In this example, the ETL contains a polycyclic aromaticelectron-transporting compound corresponding to an isomeric mixture offluoranthene derivatives. One can see from Table 11 that devices whichcontain inventive compound Inv-3 show significant lower drive voltageand higher efficiency relative to the comparative devices (12.1).

EXAMPLE 13 Preparation of Blue-light Emitting Devices 13.1 through 13.6

A series of OLED devices (13.1 through 13.6) were constructed in thefollowing manner:

-   -   1. A glass substrate coated with an 85 nm layer of indium-tin        oxide (ITO), as the anode, was sequentially ultrasonicated in a        commercial detergent, rinsed in deionized water and exposed to        oxygen plasma for about 1 min.    -   2. Over the ITO was deposited a 1 nm fluorocarbon (CF_(x))        hole-injecting layer (HIL) by plasma-assisted deposition of CHF₃        as described in U.S. Pat. No. 6,208,075.    -   3. Next a layer of hole-transporting material        4,4′-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) was        deposited to a thickness of 95.0 nm.    -   4. A 20 nm light-emitting layer (LEL) corresponding to a host        material, P-4 and 1.5% by volume of dopant FD-54 was then        deposited.    -   5. A 35.0 nm electron-transporting layer (ETL) corresponding to        P-4 and Inv-1 (see Table 12 for levels) was vacuum over the LEL.    -   6. An electron-injecting layer (EIL) corresponding to LiF at a        thickness of was 0.5 nm was vacuum deposited onto the ETL layer.    -   7. And finally, a 100 nm layer of aluminum was deposited onto        the EIL, to form the cathode.

The above sequence completes the deposition of the EL device. The devicewas then hermetically packaged in a dry glove box for protection againstambient environment.

During their preparation each device was duplicated to give fouridentically fabricated devices for each example. The devices thus formedwere tested for drive voltage and luminous efficiency at an operatingcurrent of 20 mA/cm². The results from the four duplicate devices wereaveraged and the results are reported in Table 12.

TABLE 12 Results for devices 13.1 through 13.6. ETL ETL Host Co-HostDrive Example (P-4) (Inv-1) Volt. Efficiency (Type) % Level % Level(Volts) (cd/A) 13.1 100 0 10.9 0.9 (Comparative) 13.2 90 10 9.2 2.2(Inventive) 13.3 75 25 6.7 3.6 (Inventive) 13.4 50 50 5.0 5.4(Inventive) 13.5 25 75 4.7 5.6 (Inventive) 13.6 0 100 4.9 5.2(Inventive)

Example 13 demonstrates the use of Inv-1 in the ETL in combination withelectron-transporting anthracene derivative, P-4. The EIL contains LiF.As can be seen from Table 12, when P-4 is used without Inv-1 in device13.1 the result is very low efficiency and high drive voltage. As thepercentage of Inv-1 in the ETL increases (device 13.2-13.5), the drivevoltage decreases and the luminance increases. In this format optimumperformance is obtained in device 13.5, which shows a synergistic effectdue to the mixture of P-4 and Inv-1 relative to device 13.1 (only P-4 inthe ETL) and device 13.6 (ETL having only Inv-1).

EXAMPLE 14 Preparation of Blue-Light Emitting OLED Devices 14.1 through14.6

A series of OLED devices (14.1 through 14.6) were constructed in thefollowing manner:

-   -   1. A glass substrate coated with an 85 nm layer of indium-tin        oxide (ITO), as the anode, was sequentially ultrasonicated in a        commercial detergent, rinsed in deionized water and exposed to        oxygen plasma for about 1 min.    -   2. Over the ITO was deposited a 1 nm fluorocarbon (CF_(x))        hole-injecting layer (HIL) by plasma-assisted deposition of CHF₃        as described in U.S. Pat. No. 6,208,075.    -   3. Next a layer of hole-transporting material        4,4′-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) was        deposited to a thickness of 95 nm.    -   4. A 20 nm light-emitting layer (LEL) corresponding to the host        material P-4 and 1.5% by volume of FD-54 was then deposited.    -   5. An electron-transporting layer (ETL) consisting of Alq at a        thickness as shown in Table 13, was vacuum-deposited over the        LEL.    -   6. For devices 14.2 through 14.6, an electron-injecting layer        (EIL1) corresponding to Inv-1 was vacuum deposited onto the ETL        at a thickness as shown in Table 13.    -   7. A second electron-injecting layer (EIL2) corresponding to LiF        at a thickness of was 0.5 nm was vacuum deposited onto the EIL1.        For device 14.1, this layer was deposited directly on the ETL.    -   8. And finally, a 100 nm layer of aluminum was deposited onto        the EIL, to form the cathode.

The above sequence completes the deposition of the EL device. The devicewas then hermetically packaged in a dry glove box for protection againstambient environment.

During their preparation each device was duplicated to give fouridentically fabricated devices for each example (except for examples14.1 and 14.2). The devices thus formed were tested for drive voltageand luminous efficiency at an operating current of 20 mA/cm². For 14.3through 14.6 the results for the four duplicate devices were average andthe results are reported in Table 13.

TABLE 13 Performance of Devices 14.1-14.6. ETL EIL1 Drive Example (Alq)Level Volt. Efficiency (Type) Level (nm) EIL1 (nm) (Volts) (cd/A) 14.135.0 — 0.0 6.4 2.8 (Comparative) 14.2 34.0 Inv-1 1.0 6.2 2.8 (Inventive)14.3 32.5 Inv-1 2.5 6.1 2.9 (Inventive) 14.4 30.0 Inv-1 5.0 5.9 2.9(Inventive) 14.5 25.0 Inv-1 10.0 5.8 3.0 (Inventive) 14.6 15.0 Inv-120.0 5.4 3.3 (Inventive)

This example illustrates the use of Alq in the ETL, Inv-1 in the EIL1,and LIF in the EIL2. One can see from Table 13 that by adding a layer ofInv-1 between the ETL and the EIL2 (devices 14.2 through 14.6) oneobtains reduced drive voltage relative to device 14.1, which does notcontain Inv-1. All devices have the same thickness.

Example 4, Table 3 illustrates the performance of similar devices inwhich the ETL is a fluoranthene derivative. By comparison, devices4.2-4.6 afford higher luminance and lower drive voltage relative todevices 14.2-14.6, indicating a better synergy between an EIL1containing Inv-1 and an ETL containing polycyclic aromatic hydrocarbons(FA-2/FA-3) relative to the case where the ETL contains theorganometallic compound Alq.

EXAMPLE 15 Preparation of Blue-light Emitting Devices 15.1 through 15.6

A series of OLED devices (15.1 through 15.6) were constructed in thefollowing manner:

-   -   1. A glass substrate coated with an 85 nm layer of indium-tin        oxide (ITO), as the anode, was sequentially ultrasonicated in a        commercial detergent, rinsed in deionized water and exposed to        oxygen plasma for about 1 min.    -   2. Over the ITO was deposited a 1 nm fluorocarbon (CF_(x))        hole-injecting layer (HIL) by plasma-assisted deposition of CHF₃        as described in U.S. Pat. No. 6,208,075.    -   3. Next a layer of hole-transporting material        4,4′-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) was        deposited to a thickness of 95.0 nm.    -   4. A 20 nm light-emitting layer (LEL) corresponding to a host        material P-4 and 1.5% by volume of dopant FD-54 was then        deposited.    -   5. A 35.0 nm electron-transporting layer (ETL) corresponding to        FA-5 and Inv-1 (see Table 14 for levels) was vacuum over the        LEL.    -   6. An electron-injecting layer (EIL) corresponding to LiF at a        thickness of was 0.5 nm was vacuum deposited onto the ETL layer.    -   7. And finally, a 100 nm layer of aluminum was deposited onto        the EIL, to form the cathode.

The above sequence completes the deposition of the EL device. The devicewas then hermetically packaged in a dry glove box for protection againstambient environment.

During their preparation each device was duplicated to give fouridentically fabricated devices for each example. The devices thus formedwere tested for drive voltage and luminous efficiency at an operatingcurrent of 20 mA/cm². The results from the four duplicate devices wereaveraged and the results are reported in Table 14.

TABLE 14 Results for devices 15.1 through 15.6. ETL ETL Host Co-HostDrive Example (FA-5) (Inv-1) Volt. Efficiency (Type) % Level % Level(Volts) (cd/A) 15.1 80 20 5.0 6.4 (Comparative) 15.2 70 30 5.0 6.3(Inventive) 15.3 60 40 5.0 6.4 (Inventive) 15.4 50 50 4.9 6.5(Inventive) 15.5 40 60 4.8 6.3 (Inventive) 15.6 30 70 4.9 6.2(Inventive)

Example 15 demonstrates the use of a mixture of FA-5 and Inv-1 in theETL, and LIF in the EIL. Devices are obtained with excellent efficiencyand low drive voltage.

EXAMPLE 16 Preparation of Blue-Light Emitting Devices 16.1 through 16.3

A series of OLED devices (16.1 through 16.3) were constructed in thefollowing manner:

-   -   1. A glass substrate coated with an 85 nm layer of indium-tin        oxide (ITO), as the anode, was sequentially ultrasonicated in a        commercial detergent, rinsed in deionized water and exposed to        oxygen plasma for about 1 min.    -   2. Over the ITO was deposited a 1 nm fluorocarbon (CF_(x))        hole-injecting layer (HIL) by plasma-assisted deposition of CHF₃        as described in U.S. Pat. No. 6,208,075.    -   3. Next a layer of hole-transporting material        4,4′-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) was        deposited to a thickness of 95.0 nm.    -   4. A 35 nm light-emitting layer (LEL) corresponding to host        material P-4 (98.5% by volume) and dopant FD-54 (1.5% by volume)        was then deposited.    -   5. An electron-transporting layer (ETL) corresponding to FA-1 at        a thickness of 30 nm was vacuum-deposited over the LEL.    -   6. A first electron-injecting layer (EIL1) corresponding a        mixture of FA-2 and FA-3; C-2; or C-3 as listed in Table 15 was        vacuum deposited onto the ETL at a thickness of 5 nm.    -   7. A second electron-injecting layer (EIL2) corresponding to LiF        at a thickness of was 0.5 nm was vacuum deposited onto the ETL1        layer.    -   8. And finally, a 100 nm layer of aluminum was deposited onto        the EIL2, to form the cathode.

The above sequence completes the deposition of the EL device. The devicewas then hermetically packaged in a dry glove box for protection againstambient environment.

The devices thus formed were tested for drive voltage and luminousefficiency at an operating current of 20 mA/cm².

TABLE 15 Results for devices 16.1 through 16.3. Example Drive Volt.Efficiency (Type) EIL1 (Volts) (cd/A) 16.1 FA-2/FA-3 9.6 0.13(Comparative) 16.2 C-2 9.5 0.05 (Comparative) 16.3 C-3 8.7 0.29(Comparative)

As can be seen from Table 15, when a device is constructed having anelectron-injecting layer containing a fluoranthene compound such asFA-2/FA-3, C-2 or C-3 that is not of the present invention, one obtainsalmost no luminance from the device and the drive voltage is high.

EXAMPLE 17 Preparation of Blue-Light Emitting Devices 17.1 through 17.6

A series of OLED devices (17.1 through 17.6) were constructed in thefollowing manner:

-   -   1. A glass substrate coated with an 85 nm layer of indium-tin        oxide (ITO), as the anode, was sequentially ultrasonicated in a        commercial detergent, rinsed in deionized water and exposed to        oxygen plasma for about 1 min.    -   2. Over the ITO was deposited a 1 nm fluorocarbon (CF_(x))        hole-injecting layer (HIL) by plasma-assisted deposition of CHF₃        as described in U.S. Pat. No. 6,208,075.    -   3. Next a layer of hole-transporting material        4,4′-Bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) was        deposited to a thickness of 95.0 nm.    -   4. A 35 nm light-emitting layer (LEL) corresponding to host        material P-4 (98.5% by volume) and dopant FD-54 (1.5% by volume)        was then deposited.    -   5. An electron-transporting layer (ETL) corresponding to P-4 at        a thickness as shown in Table 16 was vacuum-deposited over the        LEL.    -   6. For devices 17.2-17.6, a first electron-injecting layer        (EIL1) corresponding Inv-1 at a level as listed in Table 16 was        vacuum deposited onto the ETL.    -   7. A second electron-injecting layer (EIL2) corresponding to LiF        at a thickness of was 0.5 nm was vacuum deposited onto the EIL1        layer. For device 17.1, this layer was deposited directly on the        ETL.    -   8. And finally, a 100 nm layer of aluminum was deposited onto        the EIL2, to form the cathode.

The above sequence completes the deposition of the EL device. The devicewas then hermetically packaged in a dry glove box for protection againstambient environment.

During their preparation each device was duplicated to give fouridentically fabricated devices for each example. The devices thus formedwere tested for drive voltage and luminous efficiency at an operatingcurrent of 20 mA/cm². The results from the four duplicate devices wereaveraged and the results are reported in Table 16.

TABLE 16 Results for devices 17.1 through 17.6. ETL EIL1 Example P-4Inv-1 Drive Volt. Efficiency (Type) Level (nm) Level (nm) (Volts) (cd/A)17.1 35.0 — 9.9 0.57 (Comparative) 17.2 34.0 1.0 6.4 3.7 (Inventive)17.3 32.5 2.5 5.3 4.9 (Inventive) 17.4 30.0 5.0 5.4 5.2 (Inventive) 17.525.0 10.0 5.5 4.6 (Inventive) 17.6 15.0 20.0 5.5 4.1 (Inventive)

Example 17 illustrates the use of an ETL containing the anthracene P-4.Comparison device 17.1 employs a LiF electron injection layer and onecan see from Table 16 that the device has high drive voltage and verylow luminance. Inventive devices 17.2-17.6 incorporate an EIL1containing Inv-1 and an EIL2 having LiF, and the corresponding devicesafford much lower drive voltage and higher luminance relative to thecomparative device. All devices have the same overall thickness.

The entire contents of the patents and other publications referred to inthis specification are incorporated herein by reference. The inventionhas been described in detail with particular reference to certainpreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

PARTS LIST

-   -   100 OLED    -   110 substrate    -   120 anode    -   130 hole-injecting layer (HIL)    -   132 hole-transporting layer (HTL)    -   134 light-emitting layer (LEL)    -   135 hole-blocking layer (HBL)    -   136 electron-transporting layer (ETL)    -   138 electron-injecting layer (EIL)    -   140 cathode    -   150 voltage/current source    -   160 electrical connectors

1. An OLED device comprising a cathode, an anode, and havingtherebetween a light-emitting layer and further comprising a first layerbetween the light-emitting layer and the cathode containing afluoranthene compound comprising one and only one fluoranthene nucleusand having no aromatic rings annulated to the fluoranthene nucleus, thefluoranthene nucleus having independently selected aromatic groups inthe 7,10-positions and an azine group in the 8- or 9-position, providedthat the azine group is not a phenanthroline group, wherein the firstlayer is an electron-transporting layer or an electron-injecting layer.2. The OLED device of claim 1, wherein the azine group contains no morethan two fused rings.
 3. The OLED device of claim 1, wherein thefluoranthene compound contains less than 10 fused aromatic rings.
 4. TheOLED device of claim 1, wherein the azine group is selected from thegroup consisting of a pyridine group, a pyrimidine group, and a pyrazinegroup.
 5. The OLED device of claim 1, wherein the fluoranthene compoundis represented by Formula (I),

wherein: Ar₁ and Ar₂ each independently represent an aromatic ringgroup; R₁-R₇ independently represent hydrogen or a substituent group;and Az represents an azine group, which can be further substituted; andprovided that two adjacent R₂-R₇ substituents, Ar₁ and R₁, and Ar₂ andAz cannot join to form an aromatic ring system fused to the fluoranthenenucleus.
 6. The OLED device of claim 5, wherein Ar₁ and Ar₂ eachrepresent an independently selected aryl ring group having 6 to 24carbon atoms, R₁-R₇ are individually selected from hydrogen, alkylgroups having 1-24 carbon atoms, and aryl groups having 6-24 carbonatoms.
 7. The OLED device of claim 5, wherein Az represents a pyridinering group and wherein the pyridine ring group contains no more than twofused rings.
 8. The OLED device of claim 6, wherein Az represents apyrid-3-yl or pyrid-4-yl group containing no fused rings.
 9. The OLEDdevice of claim 1, wherein the fluoranthene compound is represented byFormula (II),

wherein: R₁-R₇ each independently represent hydrogen or a substituentgroup, provided that two adjacent R₂-R₇ substituents cannot join to forman aromatic ring system fused to the fluoranthene nucleus; R is asubstituent; provided adjacent substituents can join to form a ringgroup; n and m are independently 0-5; and Az represents an azine group.10. The OLED device of claim 9, wherein Az is selected from the groupconsisting of:


11. The OLED device of claim 1,wherein the thickness of the first layeris 10 nm or less.
 12. The OLED device of claim 1, wherein: a) the firstlayer includes an alkali metal or alkali metal compound; or b) wherein asecond layer, located between the first layer and the cathode andcontiguous to the first layer, contains an alkali metal or an alkalimetal compound; and c) provided that both the first and second layerscan contain an independently selected alkali metal or alkali metalcompound.
 13. The OLED device of claim 12, wherein the alkali metalcompound comprises LiF or an organic lithium compound represented byFormula (III),(Li⁺)_(m)(Q)_(n)  Formula (III) wherein: Q is an anionic organic ligand;and m and n are independently selected integers selected to provide aneutral charge on the complex.
 14. The OLED device of claim 1, wherein:a) the first layer includes, in addition to the fluoranthene compound, apolycyclic aromatic hydrocarbon compound; or b) a third layer, locatedbetween the first layer and the light-emitting layer and contiguous tothe first layer, includes the polycyclic aromatic hydrocarbon compound,provided that both the first and third layers can include anindependently selected polycyclic aromatic hydrocarbon compound; andwherein, c) the polycyclic aromatic hydrocarbon compound comprises atleast 3 fused aromatic rings and the absolute difference in LUMO energyvalues between the polycyclic aromatic hydrocarbon compound and thefluoranthene compound is 0.3 eV or less.
 15. The OLED device of claim14, wherein the third layer includes an alkali metal or alkali metalcompound.
 16. The OLED device of claim 14, wherein the polycyclicaromatic hydrocarbon compound comprises an anthracene derivative ofFormula (IV),

wherein: R¹ and R⁶ each independently represent an aryl group having6-24 carbon atoms; and R²-R⁵ and R⁷-R¹⁰ are each independently chosenfrom hydrogen, alkyl groups having from 1-24 carbon atoms and aromaticgroups having from 6-24 carbon atoms.
 17. The OLED device of claim 14,wherein the polycyclic aromatic hydrocarbon compound comprises afluoranthene derivative of Formula (V),

wherein: R¹¹-R²⁰ are independently chosen from hydrogen, alkyl groupshaving from 1-24 carbon atoms, and aromatic groups having from 6-24carbon atoms, provided adjacent groups can combine to form fusedaromatic rings.
 18. The OLED device of claim 17, wherein R¹¹ and R¹⁴represent independently selected aryl groups having 6-24 carbon atoms;and R¹², R¹³ and R¹⁵-R²⁰ are independently chosen from hydrogen, alkylgroups having from 1-24 carbon atoms and aromatic groups having from6-24 carbon atoms, provided adjacent groups cannot combine to form fusedaromatic rings.
 19. An OLED device comprising a cathode, an anode, andhaving there between a light-emitting layer and further comprising: a) afirst layer between the light-emitting layer and the cathode containinga fluoranthene compound comprising one and only one fluoranthene nucleusand having no aromatic rings annulated to the fluoranthene nucleus, thefluoranthene nucleus having independently selected aromatic groups inthe 7,10-positions and an azine group in the 8- or 9-position, providedthat the azine group is not a phenanthroline group, wherein the firstlayer is an electron-transporting layer or an electron-injecting layer;b) a second layer between the first layer and the cathode and contiguousto the first layer, wherein the second layer includes an alkali metal oralkali metal compound; and c) a third layer between the first layer andthe light-emitting layer and contiguous to the first layer, wherein thethird layer includes a polycyclic aromatic hydrocarbon compound havingat least 3 fused aromatic rings and wherein the absolute difference inLUMO energy values between the polycyclic aromatic hydrocarbon compoundand the fluoranthene compound is 0.3 eV or less.
 20. The OLED device ofclaim 19, wherein the azine group contains no fused rings; and thepolycyclic aromatic hydrocarbon compound comprises a9,10-diarylanthracene group or a 7,10-diaryl substituted fluoranthenegroup having no aromatic rings annulated to the fluoranthene nucleus.